Accelerated Drying Concrete Compositions and Methods of Manufacturing Thereof

ABSTRACT

Cementitious compositions and processes for preparing and using the cementitious compositions are provided. The cementitious compositions are characterized by the property of a reduced or an attenuated water vapor emission from a cementitious mix and a concrete formed therefrom. Certain cementitious compositions are characterized by the property of accelerated drying while still maintaining good workability. Methods of improving water retention and surface drying of concrete, including lightweight concrete are provided. A water soluble ionic salt may be used to sequester water within the pores and capillaries of the cement paste and/or porous lightweight aggregate. In some examples, the salt may be added directly to concrete or aggregates may be infused with a water-salt solution to provide treated porous aggregates having improved water saturation and water retention.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/947,715 filed Jul. 22, 2013, which is a continuation of U.S.application Ser. No. 13/062,603 filed May 16, 2011, now U.S. Pat. No.9,133,058, which is a U.S. National Phase filing of InternationalApplication No. PCT/US2010/042109 filed Jul. 15, 2010, which is acontinuation of U.S. application Ser. No. 12/503,610 filed Jul. 15,2009, the contents of each of which are fully incorporated herein byreference. This application also claims priority to U.S. ProvisionalApplication Ser. Nos. 61/673,927 filed Jul. 20, 2012 and 61/709,428filed Oct. 4, 2012, the contents of each of which are fully incorporatedherein by reference. This application also claims priority toInternational Application No. PCT/US2013/051356 filed Jul. 19, 2013.

FIELD OF INVENTION

The present invention is directed to concrete compositions. Variousembodiments of the present invention relate to cementitious compositionsused in preparing a concrete having an attenuated or decreased rate ofwater vapor emissions after hardening. Other embodiments of theinvention relate to cementitious compositions that are accelerateddrying concrete compositions. Yet other embodiments of the inventionrelate to concrete including low-density concrete that enhance waterretention and/or provide accelerated drying of such concrete. Certainembodiments of the invention also relate to methods of preparing andusing the cementitious and concrete compositions of the invention.

BACKGROUND OF THE INVENTION

Concrete is a composite construction material composed primarily of thereaction products of hydraulic cement, aggregates, and water. Water isboth a reactant for the cement component and is necessary to providedesired flow (e.g., spread and/or slump) characteristics and ensureconsolidation of freshly mixed concrete to prevent formation ofstrength-reducing voids and other defects. Chemical admixtures may beadded to freshly mixed concrete to modify characteristics such asrheology (i.e., plastic viscosity and yield stress), water retention,and set time. Although some of the water reacts with the cementcomponent to form crystalline hydration products, a substantial portionremains unreacted and is typically removed from concrete by evaporation.The continued evaporation of water from concrete can pose problems,particularly when applying a floor covering.

A cementitious composition for forming concrete generally refers to amixture of natural and/or artificial aggregates, such as, for example,sand and either a gravel or a crushed stone, which are held together bya binder of cementitious paste to form a highly durable buildingmaterial. The paste is typically made up of a hydraulic cement, such asPortland cement, and water and may also contain one or more chemicaladmixtures as well as supplementary cementing materials, such as, forexample, fly ash or ground granulated blast furnace slag cement.

Early cements were based on calcined lime, which is produced by exposinglimestone at an elevated temperature, for example, a temperature well inexcess of 800° C., in the presence of an oxygen-containing atmosphere toform quick-lime according the reaction in equation (1).

CaCO₃CaO+CO₂(g)  (1)

Hydraulic limes are derived from calcined limes that have some amount ofclay. The clay provides silicon and aluminum that react with the calciumfrom the limestone to produce cements having complex compounds thathydrate. These compositions even have the ability to harden underwater.Portland cement eventually evolved from these materials.

Most conventional construction cements are hydraulic, many of which arebased on Portland cement. Hydraulic cements set and harden after beingcombined with water, as a result of chemical reactions induced by thewater, and demonstrate an improved strength and stability afterhardening.

The discontinued use of volatile components in floor covering adhesivesfor concrete surfaces has created bonding and delamination problems.Concrete contains water for cement hydration as well as water ofconvenience to facilitate workability and placement. The water is bothchemically bound and entrapped in gel and small capillaries comprisingabout 30-50% of the paste material depending upon maturity. Water inconcrete must be consumed, sequestered or evaporated into the atmospherebefore a proper, permanent water-based adhesive bond can be assured.Unfortunately, the time necessary to accommodate the requisite dryingprocess is approximately one month per inch of concrete floor depth forstandard weight concrete.

Setting and hardening of hydraulic cements is caused by hydrationreactions that occur between the compounds that make up the cement andwater, which result in the formation of hydrates or hydrate phases. Thecementitious composition begins to progressively stiffen leading to theonset of setting, where additional consolidation of the hydrationreactants occurs. Hardening follows setting, which is characterized by asteady growth in the compressive strength of the material over a periodthat can range from a few days in the case of “ultra-rapid-hardening”cements to several years in the case of ordinary cements.

Portland cement consists of five major compounds as well as someadditional minor compounds. The major compounds are tricalcium silicate,3CaO.SiO₂; dicalcium silicate, 2Ca.SiO₂; tricalcium aluminate,3CaO.Al₂O₃; tetracalcium aluminoferrite, 4CaO.Al₂O₃.Fe₂O₃; and gypsum,CaSO₄.2H₂O. The hydration of tricalcium silicate is represented by thereaction according to equation (2).

2(3CaO.SiO₂)+11H₂O→3CaO.2SiO₂.8H₂O+3Ca(OH)₂  (2)

Upon the addition of water, the reaction rapidly progresses to releasecalcium and hydroxide ions. Once the water solution becomes saturated,the calcium hydroxide begins to precipitate forming a crystallinestructure. Calcium silicate hydrate is also simultaneously formed. Asthe calcium hydroxide precipitates from solution, the tricalciumsilicate continues to go into solution to form calcium and hydroxideions. The reaction is somewhat exothermic involving the evolution ofheat as the reaction progresses.

The formation of calcium hydroxide and calcium silicate hydrate provides“seeds” around which calcium silicate hydrate may continue to form. At acertain point, the rate of reaction finally becomes controlled by therate of diffusion of water molecules through the layer of calciumsilicate hydrate that surrounds the unreacted tricalcium silicate, whichprogressively becomes slower as the layer of calcium silicate hydrategrows larger.

Dicalcium silicate is hydrated to form the same products as tricalciumsilicate according to the reaction in equation (3).

2(2CaO.SiO₂)+9H₂O→CaO.2SiO₂.8H₂O+Ca(OH)₂  (3)

However, the hydration of dicalcium silicate occurs much more slowly andis mildly exothermic in comparison to that for tricalcium silicate.

The reactions of the other major components of Portland cement are morecomplex and beyond the scope of the background discussion given here.However, the hydration of cement is typically characterized by fivedistinct phases. Phase I is characterized by rapid hydrolysis of thecement compounds and can result in a temperature increase of severaldegrees over a period lasting on the order of 15 minutes or longer. Theevolution of heat begins to dramatically slow in phase II, the dormancyperiod, which can extend from one to three hours. In phases III and IV,the concrete begins to harden and the evolution of heat begins toincrease due primarily to the continued hydration of tricalciumsilicate. These phases can encompass a period of up to approximately 32to 36 hours. Stage V marks a period of continued hydration, but at muchlower rates than experienced in the earlier phases, and continues aslong as unreacted water and unhydrated silicates remain and can come incontact with one another. Stage V typically continues on the order ofdays, if not longer.

More commonly, modern-day cements are formulations of hydraulic cementblends. For example, a hydraulic cement, such as, for example, Portlandcement, can comprise up to 75% of ground granulated blast furnace slag.The slag results in a reduction in early strength but provides increasedsulfate resistance and diminished heat evolution during the stiffeningand hardening stages of the concrete.

Blended hydraulic cements can comprise one or more pozzolan materials,which are siliceous or aluminosiliceous materials that demonstratecementitious properties in the presence of calcium hydroxide. Thesilicates and even aluminates of a pozzolan reacting with the calciumhydroxide of a cement form secondary cementitious phases (e.g., calciumsilicate hydrates having a lower calcium to silicon ratio), whichdemonstrate gradual strengthening properties that usually begin to berealized after 7 days of curing.

Blended hydraulic cement may comprise up to 40% or more fly ash, whichreduces the amount of water that must be blended with the cementitiouscomposition, allowing for an improvement in early strength as theconcrete cures. Other examples of pozzolans that can be used inhydraulic cement blends include a highly reactive pozzolan, such as, forexample, silica fume and metakaolin, which further increases the rate atwhich the concrete gains strength resulting in a higher strengthconcrete. Current practice permits up to 40 percent or higher reductionin the amount of hydraulic cement used in the concrete mix when replacedwith a combination of pozzolans that do not significantly reduce thefinal compressive strength or other performance characteristics of theresulting concrete.

A lightweight coarse aggregate is frequently designed into a concretemix to reduce building dead load, enable longer spans, provide betterseismic benefits, increase fire resistance, and improve soundinsulation. This lightweight material commonly comprises expanded shale,clay, pumice, cinders or polystyrene with a density of about ½ or lessthan that of normal stone coarse aggregate and is capable of producingconcrete that weighs from 800 to 1000 pounds less per cubic yard.

In general, the weight reduction in the lightweight aggregate isachieved by creating a highly porous internal structure that can,unfortunately, also absorb up to 30% water. This water is in addition tothe normal water of convenience and can impart an additional amount tothe concrete mix equal to 2-3 times that which must normally be consumedand evaporated, thereby further increasing the time-to-dry for adhesiveor epoxy application. To prevent workability losses due to waterabsorption during mixing, transport and placement, porous aggregatesmust be pre-conditioned with water.

Should the concrete be conveyed to the location of placement by aconcrete pump, water absorption by the porous aggregates becomes morecritical, since the concrete may be subjected to liquid pressure withinthe pump and attendant line of up to 1000 psi (69 bar), which greatlycompresses the air in the pores and causes significant additional waterabsorption. Such pressure can force water required for workability intothe previously unsaturated pores of the lightweight aggregates (i.e.,pores which are not filled when subjected to atmospheric pressure butwhich can be filled at high pressures associated with pumping). Thus,complete saturation of the pores of lightweight aggregates is preferredto prevent workability loss and potential pump line obstructions underthese conditions.

Unfortunately, complete saturation is impractical since prolongedsoaking in water will not displace air trapped within the capillaries ofthe lightweight aggregate, so some loss of mix water during conveyancehas to be tolerated. Moreover, water instilled into porous aggregatesmay quickly evaporate in storage, returning the lightweight aggregatelargely to its previous dry condition within days. Thus, pre-wettedaggregates must be used almost immediately to capture the desiredbenefit.

Moreover, even these methods often do not typically result in fullysaturated capillaries. Any remaining empty capillaries, when subjectedto pump pressures, partially fill with water in response, compressingthe air trapped in the capillaries of the lightweight in accord with theUniversal Gas Law, thus resulting in the aforementioned workabilitylosses and potential line clogging during pumping. This can have severalconsequences: additional water must be added to the concrete mix priorto pumping to maintain workability sufficient to facilitate pumping.Thereafter, when the concrete exits the pump and returns to normalatmospheric pressure, the excess water responds to the compressed airwithin the lightweight aggregates and is partially forced back out intothe mix. This, in effect, increases the water-to-cement ratio,excessively diluting the plastic concrete mix and impacting the hardenedconcrete's permeability.

The cementitious materials in concrete require water, typically known aschemical water or hydration water, to chemically evolve into a hard,crystalline binder. For example, Portland cements generally require upto about 40% of their weight in water in order to promote completehydration and chemical reaction.

Excess water has conventionally been added to make concrete more plasticallowing it to flow into place. This excess water is known as water ofconvenience. A small amount of the water does escape as a result ofsolids settling during the plastic phase, evaporation at the atmosphericinterface, and absorption into accepting interface materials. However,much of the water of convenience remains in the concrete during andimmediately following hardening. The water of convenience can thenescape into the atmosphere following the hardening of the concrete. Thewater of convenience, depending on, among other things, the water tocementitious ratio, may represent up to about 70% of the total water inthe concrete.

The concrete construction and floor-covering industries may incur bothconstruction delays and remedial costs as a result of water vaporemissions and water intrusion from concrete. For example, adhesives andcoatings used in the construction of concrete floors are relativelyincompatible with moisture that develops at the concrete surface.Moisture may also create an environment for promoting the growth ofmold.

Water tightness in concrete structures is a measure of the ability ofthe hardened concrete to resist the passage of water. Water vaporemission is proportional to the state of relative dryness of the body ofthe concrete structure. Once isolated from external sources of water,water vapor emissions are derived from the amount of water that is usedin excess of that needed to harden the cementitious materials—i.e., thewater of convenience. Depending upon the atmospheric temperature andhumidity at the surface and the thickness of the concrete, theelimination of excess water through water vapor emissions can take onthe order of many months to reach a level that is compatible with theapplication of a coating or an adhesive.

There is also a possibility that water may develop under the floor dueto flooding, water backup, etc. A hardened concrete that resists watervapor permeation is capable of further protecting any coatings that havebeen applied to the surface of the concrete. There is a need in the artfor a concrete that, once it becomes hardened, is substantiallyresistant to water vapor permeation.

Installation of an impermeable barrier on the surface of the concreteprior to reaching an acceptable level of dryness may result in moistureaccumulation, adhesive failure, and a consequential failure of thebarrier due to delamination. Premature application of coatings andadhesives increases the risk of failure, while the delay caused bywaiting for the concrete to reach an acceptable level of dryness mayresult in potentially costly and unacceptable construction delays.

The floor covering industry has determined, depending on the type ofadhesive or coating used, that a maximum water vapor emission rate offrom 3 to 5 pounds of water vapor per 1,000 square feet per 24 hourperiod (lb/1000 ft²·24 hr) is representative of a state of slab drynessnecessary before adhesive may be applied to the concrete floor.

There remains a need in the art for cementitious compositions thatreduce the amount of time needed to reach a desired water vapor emissionrate in concrete floors enabling a more timely application of coatingsand adhesives.

It is known in the art that certain polymers classified assuperplasticizers may be included in concrete in order to reduce theamount of water of convenience needed to allow the cementitious mix tomore readily flow into place. Certainly, a reduction in the amount ofexcess water remaining after the concrete hardens should lead to areduction in the amount of time necessary to reach a desired water vaporemissions rate. However, the use of superplasticizers alone does notaddress other effects that influence the rate of water vapor emissionfrom the concrete.

There remains a need in the art for cementitious compositions thatfurther reduce the amount of time necessary to reach a desired watervapor emission rate in concrete floors beyond that which is achievedthrough a reduction in the amount of water required through the use of asuperplasticizer additive.

If attainment of a faster drying lightweight concrete is an objective,the usual method of water reduction by utilizing large doses ofsuper-plasticizers (very high range water reducers) is difficult becauseof the sensitivity of the mix to the loss of the enhanced efficiencywater. Furthermore, high doses of super plasticizers tend to impart athixotropic characteristic exhibited by workability loss if deprived ofmixing shear. This loss of mixing shear often occurs during pump hosemovement or delay in concrete supply. Because the efficiency ofadmixture-treated water is improved, loss of water by temporaryabsorption into the pores of lightweight aggregates during pressurizedpumping has both a substantially greater negative impact on workabilityand a greater negative impact causing potential segregation and bleedingwhen the admixture-treated water is released from the pores of theaggregates after exiting the pump.

Similarly, the inclusion of silica fume or metakaolin both well-known,highly reactive pozzolans, possess very high surface areas and thereforeagain require super-plasticizer to reduce water and maintainworkability. It also has been found that highly super-plasticizedconcrete is more difficult to air entrain. Air entrainment is animportant feature of lightweight concrete, since it aids in reducingweight and lowers the mortar density thereby attenuating the tendency ofthe coarse lightweight aggregate particles to float to the surface andhinder finishing operations.

The absorbed water and resulting added mixture water caused by pumpingconcrete containing porous lightweight aggregates therefore posesdifficulties when accelerated drying of the concrete is desired. As aconsequence of concrete hydration and lowering of internal vaporpressure in the mortar, the additional water released from thecapillaries of the porous aggregates permeates the mortar in theconcrete. While this can be beneficial from the standpoint of promotingmore complete hydration of the cementitious binder, particularly inlower water-to-cement ratio systems, it can create a prolonged period ofrelatively high humidity within the concrete, resulting in moistconcrete that must dry out before it can be coated or sealed. Suchdrying is further retarded in humid climates.

The state of dryness within concrete is usually determined by drillingholes to accommodate in-situ humidity probes. When these probes indicatean internal relative humidity (IRH) of 75%, it is presumed to berepresentative of the future sealed equilibrium moisture condition ofthe full concrete thickness. Attainment of 75% relative humidity (somefloor coverings tolerances may be slightly more or less) ensures thatthe concrete surface is ready for adhesive application. Experience inthe floor covering industry has validated research data which indicatesthat if internal humidity probes are inserted to a depth of 40% of aconcrete structure having one side exposed to the atmosphere (20% if twosides are exposed) in accordance with ASTM F-2170-09, “Standard Methodfor Determining Humidity in Concrete Floor Slabs Using in-situ Probes”,and the probes indicate an internal relative humidity of 75%, that thisis representative of the sealed future equilibrium moisture condition ofthe full thickness. If the internal relative humidity is higher than75%, it is assumed the floor will not accept water based glue and willgenerate sufficient vapor pressure to delaminate impervious coatings.Below that amount, and absent outside moisture influences, it is assumethe structure can accept water based glue and not generate sufficientvapor pressure differential to de-bond impervious coatings. Epoxysealers are also sensitive to water vapor pressure and consequently,encounter similar problems. Premature application of eitherwater-soluble adhesive or epoxy sealer to under-dried concrete canresult in moisture accumulation beneath the applied impervious surfaceand a potential for loss of bond with the epoxy or flooring. There aresealers that can be applied to attenuate the water vapor emission, butthey often fail, resulting in loss of space utilization during repairand occasionally creating costly litigation. To reduce the risk of suchproblems, floors with excessive humidity may require drying times of upto a year or more.

The substitution of the porous lightweight aggregates which absorb waterinstead of normal aggregates can prolong drying times by months or ayear or more. Research has demonstrated that high performance standardweight coarse aggregates concrete (HPC) can dry to satisfactory IRHcondition comparatively rapidly. These concretes have water-cementitiousratios (W/Cs) generally below 0.40 and contain fairly large amounts ofcement or cement/pozzolans to achieve an internal relative humidity of75% as ascertained by ASTM F 2170 “Determining Relative Humidity inConcrete Slabs Using in situ probes.” An example the large waterdifference is shown in Table 1 below.

TABLE 1 dry, lbs dry, lbs dry, lbs Lightweight Lightweight Normal HPCHPC Cement 300 400 400 GGBFS 200 400 400 Sand 1340 1274 1220 Stone 17501750 850 Water 325 285 325 plasticizer 10 oz. 40 oz. 40 oz. W/C 0.650.36 0.41 PCF 145 150.5 118.3 AE 1.30% 1.30% 5% Total W/C 0.70 0.39 0.60Aggregate Water 23 23 151

Other research by Suprenant and Malisch (1998) reported that a 4 inchconcrete slab made from conventional concrete required 46 days to reacha moisture vapor emission rate (MVER) of 3.0 lb/1000 ft2/24 hours. In1990 they reported that a lightweight concrete slab made with the samew/cm and cured in the same manner took 183 days to reach the same MVER,a four-fold increase.

The construction industry, therefore, faces a dichotomy. It can addresswater absorption by the porous aggregate with as much water as needed toensure pumpability and avoid critical workability loss in the pump lineand deal with the consequent prolonged drying time of up to a year oraccept the risk of floor failure by using a sealer to isolate themoisture-laden floor from an applied impervious coating or water solubleglue. The concrete construction and floor-covering industries maytherefore incur construction delays and/or remedial costs as a result ofwater vapor emissions and water intrusion from concrete. Moisture mayalso create an environment for promoting growth of mold.

BRIEF SUMMARY OF THE INVENTION

Various embodiments of the invention relate to cementitious compositionshaving an attenuated or a decreased rate of water vapor emissions from aconcrete formed therefrom. Certain embodiments of the invention aredirected to a concrete produced from certain cementitious compositionsof the invention. While not intending to be bound by theory, certainembodiments of cementitious compositions offer the improvement ofproviding a concrete that allows for the application of coatings andadhesives sooner than concretes produced by cementitious compositionsknown in the art.

In one of the various aspects of the invention, a cementitiouscomposition is provided comprising a hydraulic cement having aconcentration in a range from about 8% to about 35% by weight based on atotal weight of the cementitious composition, a finely divided materialhaving a concentration in a range from about 5% to about 40% by weightbased on the total weight of the cementitious composition, an aggregatehaving a concentration in a range from about 50% to about 85% by weightbased on the total weight of the cementitious composition, asuperplasticizer having a concentration in a range from about 4 to about16 ounces per 100 pounds of the hydraulic cement, and at least one of analkali metal halide salt, an alkali metal nitrate salt, and an alkalimetal nitrite salt having a concentration of from about 20 lb/yd³ toabout 40 lb/yd³.

In an embodiment of the invention, the aggregate of the cementitiouscomposition aggregate may comprise a fine aggregate and a courseaggregate. In certain embodiments of the invention, a ratio by weight ofthe fine aggregate to the aggregate is from about 0.25 to about 1.00.

In an embodiment of the invention, the alkali metal nitrite salt may bea sodium nitrite.

A cementitious composition of the invention may comprise a hydrauliccement; an aggregate; a superplasticizer; and at least one water solublesalt selected from the group consisting of water soluble silicates,acetates, sulfates, thiosulfates, carbonates, nitrates, nitrites,bromides, chlorides, thiocyanates, and hydroxides of one or more alkalimetals or alkaline earth metals, and mixtures thereof.

In certain embodiments of the invention, at least one water soluble saltis blended with the cementitious composition. In other embodiments ofthe invention, at least a portion of the at least one water soluble saltmay additionally be infused as an aqueous solution in the aggregate.

In certain embodiments of the invention, the at least one water solublesalt has a concentration in the aqueous solution of from about 8% toabout 20% by weight based on a total weight of the aqueous composition.According to more specific embodiments of the invention, the at leastone water soluble salt is selected from the group consisting of sodiumacetate, sodium nitrate, sodium nitrite, potassium carbonate, sodiumsulfate, potassium sulfate, sodium chloride, sodium silicate, sodiumthiosulfate hydrate, and sodium thiocynate.

In some embodiments of the invention, the aggregate is a porouslightweight aggregate.

In certain embodiments of the invention, the at least one water solublesalt comprises a sodium thiosulfate and a sodium thiocyanate. Furtherpursuant to this embodiment of the invention, the concentration of thesodium thiocyanate is from about 0.28% to about 0.55% based upon a totalweight of cementitious composition. In certain other embodiments of theinvention, a concentration of the sodium thiocyanate may be up to about0.09% by weight based upon the total weight of the cementitiouscomposition.

Another aspect of the invention provides a method of manufacturing ahardened concrete comprising preparing a fresh concrete mixture byblending together an aggregate, at least one water soluble salt,hydraulic cement and water, the water including both water of hydrationand excess water, and allowing the water of hydration to react with thehydraulic cement to form hydrated cement paste having pores andcapillaries. In certain embodiments of the invention, the at least onewater soluble salt enhances the retention of the excess water by thepores and capillaries of the cement paste and inhibits diffusion ofwater through the concrete to a surface of the hardened concrete,thereby allowing the hardened concrete to more quickly achieve a desiredinternal humidity and surface dryness compared to concrete made in theabsence of the at least one salt.

In an embodiment of the invention, the at least one water soluble saltmay be selected from the group consisting of salts of lithium,potassium, sodium, calcium, magnesium, and mixtures thereof. In certainembodiments of the invention, the at least one water soluble salt isselected from the group consisting of water soluble silicates, acetates,sulfates, thiosulfates, carbonates, nitrates, nitrites, bromides,chlorides, thiocyanates, and hydroxides of one or more alkali metals oralkaline earth metals, and mixtures thereof.

In certain embodiments of the invention, the at least one water solublesalt allows the concrete to achieve a 75% internal relative humiditywith less total evaporation of water from the concrete compared to aconcrete substantially free of the at least one water soluble salt. Inother embodiments of the invention, the at least one water soluble salthas less autogenous and/or drying shrinkage of the hardened concretecompared to a concrete substantially free of the at least one watersoluble salt. In yet other embodiments of the invention, the at leastone water soluble salt permits faster surface drying at a higherwater-cementitious materials ratio and with less superplasticizercompared to a concrete substantially free of the at least one watersoluble salt.

In certain embodiments of the invention, the aggregate may comprise aporous aggregate and the at least one water soluble salt may reduce theinflow and outflow of water from pores and capillaries of the porousaggregate in comparison to a concrete substantially free of the at leastone water soluble salt.

According to certain embodiments of the invention, the at least onewater soluble salt is added to the fresh concrete mixture upon blendingtogether the aggregate, at least one water soluble salt, hydrauliccement, and water. In certain embodiments of the invention, at least aportion of the at least one water soluble salt is indirectly added tothe fresh concrete mixture by infusing a porous lightweight aggregatewith an aqueous solution of the at least one salt prior to blendingtogether the aggregate, at least one water soluble salt, hydrauliccement, and water.

In an embodiment of the invention, infusing the porous lightweightaggregate with the aqueous solution improves workability of the freshconcrete mixture compared to a concrete made in the absence of infusingthe porous lightweight aggregate with the aqueous solution. In certainembodiments, infusing the porous lightweight aggregate with the aqueoussolution improves pumpability and decreases workability loss whenpumping the fresh concrete mixture under pressure compared to concretemade in the absence of infusing the porous lightweight aggregate withthe aqueous solution.

An additional aspect of the invention provides a concrete manufacturedaccording to any of the methods of the invention.

These embodiments of the invention and other aspects and embodiments ofthe invention will become apparent upon review of the followingdescription taken in conjunction with the accompanying drawings. Theinvention, though, is pointed out with particularity by the appendedclaims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 is a chart illustrating the percentage of water loss of porouslightweight aggregates treated by tap water (Sample 43) and solutions ofseven different salts (Samples 44-50) after drying for 27 hours;

FIG. 2 is a chart illustrating unfilled pore space of porous lightweightaggregates treated by tap water (Sample 43) and solutions of sevendifferent salts (Samples 44-50) after drying for 27 hours and then beingre-immersed for 30 minutes, as indicated by weight percent of waterneeded to fully saturate the unfilled space of the aggregates;

FIG. 3 is a chart illustrating water vapor emission of concrete madefrom aggregates treated by tap water (Sample 51) and four solutions ofdifferent salts (Samples 52-55);

FIG. 4 is a chart illustrating water vapor emission of concrete madefrom aggregates treated by tap water (Sample 56) and four solutions(Samples 57-60), wherein aggregates were soaked in water (Sample 56) orboiled in aqueous solutions (Samples 57, 58, and 59) or partially driedthen dipped in an aqueous solution of 15% NaAc and 5% NaCl (Sample 60);

FIG. 5 is a chart illustrating the close correlation between waterevaporation rate of lightweight concrete and the number of days requiredfor the concrete to reach 75% relative humidity;

FIG. 6 is a chart illustrating the number of days required forlightweight concrete containing various salts to reach 75% relativehumidity;

FIG. 7 is a chart illustrating the number of days required for normalweight concrete containing various salts to reach 75% relative humidity;

FIG. 8 is a graphical representation showing the relative humidity overtime for two exemplary embodiments of cementitious mixes of theinvention;

FIG. 9 is a chart illustrating the relative humidity over time forcementitious compositions having various concentration of sodium nitriteaccording to an embodiment of the invention;

FIG. 10 is a chart illustrating the relative humidity over time forcementitious compositions having various concentrations of sodiumnitrite according to another embodiment of the invention; and

FIG. 11 is a graphical representation showing the relative humidity overtime for cementitious compositions having various concentrations ofsodium nitrite according to

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the inventions are shown. Preferred embodiments of theinvention may be described, but this invention may, however, be embodiedin many different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Theembodiments of the invention are not to be interpreted in any way aslimiting the various inventions described herein.

Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation. Allterms, including technical and scientific terms, as used herein, havethe same meaning as commonly understood by one of ordinary skill in theart to which this invention belongs unless a term has been otherwisedefined. It will be further understood that terms, such as those definedin commonly used dictionaries, should be interpreted as having a meaningas commonly understood by a person having ordinary skill in the art towhich this invention belongs. It will be further understood that terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and the present disclosure. Suchcommonly used terms will not be interpreted in an idealized or overlyformal sense unless the disclosure herein expressly so definesotherwise.

As used in the specification and in the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contextclearly indicates otherwise. For example, reference to “a concrete”includes a plurality of such concrete.

Exemplary compositions of the invention are described in the examplespresented herein. As a person having ordinary skill in the art to whichthis invention belongs would appreciate, variations or modificationsfrom these exemplary compositions, as detailed in the specification andas further set forth in the claims that follow, are intended to beincluded within the scope of the present invention.

As used herein, “wt %” or “weight percent” or “% by weight” or “percentby weight” and any variations thereof, unless specifically stated to thecontrary, means a weight percentage of the component based on the totalweight of the composition or article in which the component is included.“Wt %” or “weight percent” or “% by weight” or “percent by weight” andany variations thereof, when referring to a cementitious mix, means aweight percentage of the component based on the total weight of thecementitious compounds in the cementitious mix or the weight of thecementitious mix on a water-free basis.

The terms “attenuated water vapor emission” or “decreasing the rate ofwater vapor emission,” as may be used interchangeably herein, as well asany variation thereof, means a cementitious composition that ultimatelyprovides a cementitious mix that produces a hardened concretedemonstrating a reduction in the amount of time needed to achieve adesired water vapor emissions rate. In an embodiment of the invention,the desired water vapor emissions rate, for example, is 3 lb/1000 ft²·24h. In certain embodiments of the invention, the attenuated water vaporemission may be measured based on the number of days required to achievea desired internal relative humidity, for example, a 75% relativehumidity.

As a person having ordinary skill in the art to which this inventionrelates would appreciate, a cementitious composition having anattenuated water vapor emission or demonstrating a decrease in the rateof water vapor emission may, depending upon the time during or aftercuring or hardening, demonstrates a smaller rate of water vaporemissions than a conventional cementitious composition.

The term “concrete structure,” as used herein, is intended to be broadlydefined to refer to any structure that is composed, in at leastsignificant part, of a concrete which has cured and hardened. A concretestructure includes, but is not limited to, a bridge, a roadway, aparking lot, a sidewalk, a curb, a parking garage, a floor, a patioslab, a support column, a pier, a marine structure, a piling, a conduitand any other paved surface whether located inside or outside.

As used herein, a “cement replacement” is a compound that partiallysubstitutes for a compound that functions as the primary cementcompound, such as, for example, a hydraulic cement, in a cementitiouscomposition. Without intending to be bound by theory, the cementreplacement itself may have binding properties similar to a cement. Assuch, any compound that can be chemically reacted or hydrolyzed by waterto ultimately form other compounds that promote the hardening of acement may, in certain embodiments, be a cement replacement. In someembodiments of the invention, the cement replacement may demonstratecementitious properties because of their mere presence with anothercomponent of cement in the cementitious composition. A pozzolan is anon-limiting example of cement replacement that demonstratescementitious properties when in the presence of another component ofcement in the cementitious composition.

In certain embodiments of the invention, a cement replacement may bechosen to impart additional properties to the cement. In a non-limitingexample, calcium carbonate may not only function as a cementreplacement, but may also act as any one of a filler, a densifier, anaccelerator of hydration, and any combination thereof. The compositionsof the invention, in certain embodiments, may include these types ofcompounds as well.

The terms “cementitious composition” or “cementitious mix” or “concretecomposition or “concrete mixture,” as may be used interchangeablyherein, refer to the final mixture that comprises the compounds intendedto be part of the formulation used to pour or cast a concrete. Suchcompositions or mixes or mixtures may refer to a composition thatincludes a cement material and, optionally, any of a pozzolan, one ormore fillers, adjuvants, additives, dispersants, and other aggregatesand/or materials that, typically upon being combined with water, form aslurry that hardens to a concrete upon curing. Cement materials include,but are not limited to, hydraulic cement, gypsum, gypsum compositions,lime and the like.

For example a cementitious composition or a cementitious mix or aconcrete composition or a concrete mixture may comprise cementitiousmaterials, optional admixtures, and aggregates. In a non-limitingexample, the cementitious mix or concrete mixture, in certainembodiments, comprises a cementitious composition and the desired amountof water. Non-limiting examples of “cementitious materials” may includehydraulic cement, non-hydraulic cement, gypsum, gypsum compositions,lime, pozzolan, granulated blast-furnace slag, and the like.

As used herein, when not otherwise specified, the term “concrete” mayrefer to the concrete mixture in either its fresh/unhardened state orits set/hardened state. A concrete in a fresh/unhardened mayadditionally be referred to as a “freshly mixed concrete,” and aconcrete in a set/hardened state may additionally be referred to as a“hardened concrete.”

The term “air entrainment” refers to the inclusion of air in the form ofvery small bubbles during the mixing of concrete. Air entrainment mayconfer frost resistance on hardened concrete or improve the workabilityof a freshly mixed concrete.

As used herein, the term “fine calcium carbonate” means a calciumcarbonate having a particle size of less than about 200 microns, lessthan about 150 microns, less than about 100 microns, and, preferably,less than about 75 microns. In certain embodiments of the invention, thefine calcium carbonate is introduced as part of a mixture that includesother compounds, such as, for example, alkaline earth and alkali metalcarbonates. Of course, another source of fine calcium carbonate islimestone, for example, the crushed limestone marketed under thetradename of limestone fines available from Omya, Inc. (Alpharetta,Ga.). Limestone fines are generally understood to be small particulatesof limestone, typically less than 65 mesh, though not intended to belimiting, generated when limestone is crushed or pulverized. In anexemplary embodiment of the invention, the fine calcium carbonate has aparticle size of less than about 75 microns and is filtered from aground mixture comprising calcium carbonate by using a standard sievesize having 75 micron openings or a varying plurality of openings of+/−75 microns.

The term “granulated blast furnace slag” refers to the glassy, granularmaterial formed when molten blast-furnace slag (a by-product of ironmanufacture) is rapidly quenched. Granulated blast furnace slag may beblended in a pulverized state with Portland cement to form hydraulicmixtures. Granulated blast furnace slag may consist essentially ofsilica, or aluminosilica glass containing calcium and other basicelements. The pulverized form of granulated blast furnace slag may alsobe referred to as “ground granulated blast furnace slag, which is alsoreferred to as “GGBFS” in certain figures provided herein.

As used herein, the term “ultrafine calcium carbonate” means a calciumcarbonate containing material having an average particle size of lessthan or equal to about 25 microns, less than or equal to about 10microns, less than or equal to about 5 microns, and, preferably, lessthan or equal to about 3 microns. In certain embodiments of theinvention, the ultrafine calcium carbonate may be introduced as part ofa mixture that includes other compounds, such as, for example, alkalineearth and alkali metal carbonates. A non-limiting example of anultrafine calcium carbonate is limestone that has been crushed andscreened having an average particle size of less than or equal to about25 microns, less than or equal to about 10 microns, less than or equalto about 5 microns, and, preferably, less than or equal to about 3microns. Any material comprising an ultrafine calcium carbonate may besuitable for use in certain embodiments of the invention.

“Internal relative humidity” (IRH) of a concrete described herein may bedetermined using the procedure developed by the ASTM committee F.06,also known as the F2170 (2002) standard entitled “In-Situ Testing ofConcrete Relative Humidity,” which is commonly used in Europe. In anexemplary representation of measuring internal relative humidity, theF-2170-02 test procedure involves drilling holes to a depth equal to 40%of the thickness of the concrete slab. The hole is partially lined witha plastic sleeve that is capped at the entrance of the hole. Theapparatus is allowed to acclimate to an equilibrium level for 72 hoursprior to inserting a probe for measuring the internal relative humidity.The floor covering industry requires the internal relative humidityreading not to exceed 75% prior to application of a flooring adhesive.

The term “pounds per cubic yard,” representing a mass based amount inpounds of a compound per cubic yard of a cementitious mix or a concrete,may also interchangeably be expressed as “lb/yd³” or “pcy.”

The term “pozzolan,” as used herein, refers to a siliceous or siliceousand aluminous material that, by itself, possesses substantially littleor no cementitious value, but when, in particular, in a finely dividedform or an ultrafinely divided form, and in the presence of water,chemically reacts with calcium hydroxide to form compounds possessingcementitious properties. Non-limiting examples of pozzolans include flyash, silica fume, micronized silica, volcanic ashes, calcined clay, andmetakaolin.

As used herein, the term “highly reactive pozzolan” are pozzolans thatreadily react with free lime to form a siliceous binder. Non-limitingexamples of highly reactive pozzolans include silica fume andmetakaolin.

The term “slump,” as used herein when referring to a cementitious mix,means the amount of subsidence of a cementitious composition.Conventionally, slump has been measured by the ASTM C143 (2008 is themost recent specification) standard test procedure, which measures theamount of subsidence of a cementitious composition after removing asupporting cone, as specified in the test procedure.

The term “shrinkage reducing agent,” as used herein, refers to an agentthat is capable of curbing the shrinkage of a cementitious mix as itcures or hardens. Non-limiting examples of shrinkage reducing agentsinclude polypropylene glycol, in particular, polypropylene glycol with anumber average molecular weight of from about 200 to about 1,500, morepreferably, from about 500 to about 1,500, and, even more preferably,from about 500 to 1,000, and derivatives of polypropylene glycol, suchas, for example, copolymers comprising polypropylene glycol(meth)acrylicacid ester and polypropylene glycol mono(meth)allyl ether. Othernon-limiting examples of polypropylene glycol derivatives includepropylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether,and the like. In certain preferred embodiments of the invention, certainspecies of polypropylene glycol in the oligomer range may act asanti-shrinkage agents for hydraulic concrete.

Plasticizers, water reducers, or dispersants, as used interchangeablyherein, are chemical admixtures that may be added to concrete mixturesto improve workability. These agents may be manufactured fromlignosulfonates.

The term “superplasticizer,” as used herein, is, generally, a waterreducer, in particular, a high-range water reducer, or an additive thatreduces the amount of water needed in a cementitious mix while stillmaintaining the workability, fluidity, and/or plasticity of thecementitious mix. Superplasticizers may include, but are not limited toformaldehyde condensates of at least one compound selected from thegroup consisting of methylolation and sulfonation products of each ofnaphthalene, melamine, phenol, urea, and aniline, examples of whichinclude metal naphthalenesulfonate-formaldehyde condensates, metalmelaminesulfonate-formaldehyde condensates, phenolsulfonicacid-formaldehyde condensate, and phenol-sulfanilic acid-formaldehydeco-condensates. Superplasticizers may also include the polymers andcopolymers obtained by polymerizing at least one monomer selected fromthe group consisting of unsaturated monocarboxylic acids and derivativesthereof, and unsaturated dicarboxylic acids and derivatives thereof.Indeed, in preferred embodiments of the invention, the superplasticizercomprises a polycarboxylate superplasticizer.

The term “polycarboxylate superplasticizer” encompasses a homopolymer, acopolymer, and any combination thereof comprising a polycarboxylic towhich other functional groups may be bonded. Preferably, these otherfunctional groups are capable of attaching to cement particles and otherfunctional groups for dispersing the attached cement particle within anaqueous environment. Specifically, polycarboxylate superplasticizers arepolymers with a carbon backbone having pendant side chains with thecharacteristic that at least a portion of the side chains are attachedto the carbon backbone through a carboxyl group or an ether group. Anexemplary polycarboxylate superplasticizer is given by Formula (I).

According to Formula (I):

D=a component selected from the group consisting of the structureaccording to Formula II, the structure according to Formula III, andcombinations thereof.

Additionally, according to Formulas (I), (II), and (III):

X=H, CH₃, C₂ to C₆ alkyl, phenyl, substituted phenyl;

Y₁=H, —COOM;

R=H, CH₃;

Y₂=H, —SO₃M, —PO₃M, —COOM, —OR₃, —COOR₃, —CH₂OR₃, —CONHR₃, —CONHC(CH₃)₂,CH₂SO₃M, —COO(CHR₄)—OH where n=2 to 6;

R₁, R₂, R₃, R₅ are each independently —(CH₂CHRO)_(m)R₄ random copolymerof oxyethylene units and oxypropylene units where m=10 to 500 andwherein the amount of oxyethylene in the random copolymer is form about60% to about 100% and the amount of oxypropylene in the random copolymeris from about 0% to about 40%;

R₄=H, methyl, C₂ to C₆ alkyl;

M=alkali metal, alkaline earth metal, ammonia, amine, methyl, C₂ to C₆alkyl;

a=0-0.8;

b=0.2-1.0;

c=0-0.5; and

d=0-0.5.

a, b, c, d, d₁, and d₂ represent the mole fraction of each unit and thesum of a, b, c, and d is 1.0. The sum of d₁ and d₂ must be equal to d.

The term “water to cementitious ratio” or “w/c” is defined as the ratioof the mass of the water to the mass of the cementitious materialsimmediately present in the cementitious mix formed upon mixing acementitious composition with the desired amount of water. Generally,when the cementitious composition also comprises a pozzolan, the mass ofthe pozzolan will be added to the mass of the cement in determining thewater to cementitious ratio. Generally, the mass of water used incalculating w/c will not include the water contained in aggregates.

The term “water-cementitious materials ratio” or “w/cm,” which may alsobe referred to as the “water-binder ratio,” is the mass ratio ofavailable water to the amount of cement plus pozzolan plus slag in apaste, mortar, or concrete.

The terms “water vapor emission rate,” “water vapor emissions rate,”“water vapor emission,” and “water vapor emissions,” as may be usedinterchangeably herein, refers to the amount of water, typicallyrepresented as mass, e.g., pounds, emitted from a 1,000 square footsurface area of concrete over a 24 hour period. The water vapor emissionrate, in an embodiment of the invention, may be measured by the testdescribed in ASTM F1869 (2004) entitled the “Standard Test Method forMeasuring Moisture Vapor Emission Rate of Concrete Sub-Floor UsingAnhydrous Calcium Chloride.” ASTM F1869 measures the vapor emission rateby placing an airtight dome containing a specified weight of calciumchloride over the hardened concrete for a defined period of time.

The term “workability,” as used herein, is the relative ease that afreshly mixed paste, mortar, or concrete may be mixed, placed,compacted, and/or finished. The homogeneity of such mixtures may alsoinfluence the workability. In certain cementitious mixtures or mortarmixtures, workability may refer to the consistency and feel of thecementitious mixture or the mortar mixture. The requisite workabilitycan vary based on the use of the cementitious and/or the mortar mixture.For example, depending on the application, the viscosity of the mixturemay vary—e.g., a higher viscosity for applications where rapidflowability is not desired or a lower viscosity where rapid flowabilityis required, such as when performs are used. Of course, as understood inthe art, other physical property parameters may also affect theworkability of the mixture.

The disclosure herein, in certain embodiments, provide composition andmethods for maintaining or altering the ionic concentration of the waterin concrete and/or lightweight aggregates in order to accommodate anamount of water in excess of that needed to react with the cements,which is typically required to provide desired workability. In general,concrete requires water for cement hydration as well as water ofconvenience to provide workability and facilitate placement. The waterof hydration must typically be consumed and the water of conveniencelargely evaporated before proper permanent bonding of water-basedadhesives can be assured. Unfortunately, the time necessary toaccommodate the requisite evaporation and hydration can be approximatelyone month per inch of concrete floor depth. Placement of floor coveringsusing current water-soluble adhesives must often be delayed until theresidual concrete water has sufficiently dissipated to provide aninternal humidity of no more than about 75%.

Generally, water vapor emission may be proportional to the state ofrelative dryness of the body of the concrete structure. Once isolatedfrom external sources of water, water vapor emissions are derived fromthe amount of water that is used in excess of that needed to harden thecementitious materials, i.e., the water of convenience. Depending uponthe atmospheric temperature and humidity at the surface and thethickness of the concrete, the elimination of excess water through watervapor emissions can take several months to reach a level that iscompatible with the application of a coating or an adhesive (e.g., toreduce risk of delamination).

A lightweight coarse aggregate may be designed into a concrete mix toreduce building dead load and increase fire resistance. This lightweightmaterial commonly comprises an expanded shale or clay with a density ofabout ½ that of normal stone coarse aggregate and is capable ofproducing lightweight concrete that weighs from 800 to 1000 pounds lessper cubic yard. The weight reduction provided by the lightweightaggregate is achieved by creating a highly porous internal structure inthe lightweight aggregate that can, however, absorb up to 30% water byweight. This water is in addition to the normal water required toprovide desired slump and can impart additional water to the concretemix equal to 2 to 3 times of the amount of water that must normallyevaporate, thereby increasing the time to dry for adhesive or epoxyapplication by a similar amount. This additional time is beyond thetolerance of many fast-track construction schedules and increases thelikelihood of bond failure and delamination should this drying time betruncated.

In certain embodiments of the invention, water soluble salts may be usedto alter the ionic concentration of the water in concrete and therebycontrol the internal relative humidity of concrete as it is drying.According to one embodiment, one or more water soluble salts areincorporated into the cement paste upon mixing the cementitiouscomponents together. According to another embodiment, one or more watersoluble salts can be incorporated into the pores of a lightweightaggregate and thereby indirectly incorporated into the cement paste whenmixing the cementitious components together. Either method allows forimproved water retention within the fine pores of the cementitiousmaterial over time, improved initial concrete workability, and limitedwater-vapor emission, enabling the resulting low-density concretes toattain a desired relative humidity in a shorter time. If water is madeavailable to the mix by virtue of its being absorbed and then desorbedby lightweight aggregate, then its introduction should be anticipated byadjusting the ionic concentration of salt added to the aggregates toyield a cement paste having a desired ionic concentration.

According to certain embodiments of the invention, autogenous and dryingshrinkage of concrete may be substantially reduced or, in certainembodiments, eliminated altogether. Finer cements, slags and pozzolansmay lead to the production of smaller pores in thecalcium-silicate-hydrate (CSH) gel. This results in increased autogenousand drying shrinkage due to the magnified effect of surface tension aspore radii diminish (Young-Laplace equation or Kelvin). As the cementparticles hydrate, they consume about 20% of their weight in water andat the same time lose about 10% of their volume, resulting in chemicalshrinkage or autogenous shrinkage. The large capillaries dry first,resulting in a shift to progressively smaller capillaries and gel pores.

Introducing salt into the capillaries and gel pores of cement pastereduces the relative humidity (RH) within concrete by virtue of the salteffect on relative humidity and its effect on the micro pore surfacetension and pressure differential across the meniscus. As a consequenceof lower w/cm and smaller pores, high performance concrete in general,and fast drying normal-weight aggregate concretes specifically, sufferfrom increased autogenous and drying shrinkage resulting in a potentialfor micro cracks and macro cracks leading to early deterioration. Thisphenomenon can be utilized to advantage in several ways. First, thesmall pores thus formed reduce the internal relative humidity (IRH) ofconcrete, particularly in the presence of increasing salt concentration.Second, if the lightweight coarse aggregate is water soaked with liquidwater (not vapor) into its capillaries, then its introduction into asoluble salt treated mortar will result in an osmotic pressure. Thispressure drives water and water vapor into the hydrated cement voidsspace, which offsets the tendency of the paste to undergo autogenous anddrying shrinkage. This is a surprising and unexpected result.

It is conventionally believed that small particles (e.g., light weightfines) are needed for moisture sourcing dispersion. However, accordingto certain embodiments of the invention, well soaked coarse lightweightaggregate in a salt-dosed HPC mix may “eliminate” drying and autogenousshrinkage. If a lightweight concrete is pumped, for instance, theexpected pressure may diminish the osmotic effect by forcing salts intothe lightweight aggregates. The drying shrinkage attenuation will remainbut autogenous shrinkage may return to significant, but diminished,extent.

This insight on shrinkage leads to new large volume uses for concrete.For example, in warehouse floor slabs or stores where concrete jointsmust be dowelled for load transfer, curling (top to bottom of slabdrying differential) pulls the slab off subgrade support and createssurface irregularities. Both shrinkages contribute to this negativeeffect. Now, in a temperature-controlled environment, expanses ofconcrete can be longer than 100 feet without a joint, leading to reducedinstallation expense in reinforcing steel and jointing. This is animportant improvement over conventional concrete methodologies forproducing fast drying concrete, particularly those which rely on largedoses of superplasticizer and low w/cm (less than 0.4), which producelarge increases in autogenous and drying shrinkages.

In certain embodiments of the invention, the water vapor emission rate,as well as other properties, such as, for example, internal relativehumidity, a required amount of water content of the concrete, and therequired water to cementitious ratio, are determined by a process orprocedure as provided in U.S. patent application Ser. No. 12/503,622issued as U.S. Pat. No. 8,220,344 entitled “Method for EstimatingProperties of Concrete” fully incorporated herein by reference. Theprocess or procedure, otherwise known as the “mortar method,” comprisesa procedure for preparing a representative mortar sample, typicallysubstantially free of any coarse aggregate, having a water tocementitious ratio that is consistent with that of the concrete to beproportioned. Preferably, the prepared mortar mixture to be tested willhave substantially the same ratio of compounds of the cementitious mix.The prepared sample mixture is cast into a small mold having a preferredsurface to volume ratio of about 0.67 in⁻¹ (6 inch×6 inch panels havinga volume of about 54 cubic inches) to simulate the drying experienced byconcrete that is exposed to the atmosphere at only one surface. Themortar is cast to a depth, which preferably approximates the depth ofconcrete that is immediately reactive to atmospheric temperature andmoisture gradients. In certain embodiments of the invention, the mortaris cast to a depth of about 1½ inches. The cast samples of mortar arecured and periodically weighed at measured intervals in order todetermine the amount of daily water loss. The water vapor loss is usedto estimate the drying rate or some other property of a concrete basedupon a correlation.

An aspect of various embodiments of the invention described hereinrelates to a cementitious composition, specifically to a cementitiouscomposition resulting in a concrete having a decreased or an attenuatedrate of water vapor emissions. The cementitious compositions areformulated to include a hydraulic cement and at least one water vaporattenuation agent. Non-limiting examples of water vapor attenuationagents include an ultrafine calcium carbonate containing material(simply referred to herein as an ultrafine calcium carbonate), having anaverage particle size of less than or equal to about 25 microns, lessthan or equal to about 10 microns, less than or equal to about 5microns, and, preferably, less than or equal to about 3 microns; ahighly reactive pozzolan; a shrinkage reducing agent; an alkali metalhalide salt; an alkali metal nitrate salt; an alkali metal nitrite salt;and at least one superplasticizer. More preferably, the at least onesuperplasticizer comprises a polycarboxylate superplasticizer. Even morepreferably, the alkali metal nitrite salt is a sodium nitrite.

In other embodiments of the invention, the cementitious compositionadditionally comprises a cement replacement. In other preferredembodiments of the invention, the cement replacement comprises a finelydivided material that comprises a material whose particle size is lessthan about 75 microns. In certain preferred embodiments of theinvention, the finely divided material comprises a finely dividedlimestone or a fine calcium carbonate. In other preferred embodiments ofthe invention, the finely divided material comprises a pozzolan, which,without intending to be limiting, reacts with water and the limereleased from cement hydration to form densifying calcium silicates. Incertain embodiments of the invention, the pozzolan may comprise anynatural pozzolan; any artificial pozzolan, such as, for example, a flyash; and any combination thereof. In yet other embodiments of theinvention, the finely divided material comprises a ground slag,preferably, a ground granulated blast furnace slag.

Another aspect of the invention provides a method of manufacturingconcrete having improved water retention and surface dryingcharacteristics, comprising: (1) preparing a fresh concrete mixture byblending an aggregate (e.g., porous lightweight aggregate) withhydraulic cement, water and one or more water soluble salts; (2)allowing water to react with hydraulic cement to form hydrationproducts, which hardens the fresh concrete mixture to form hardenedconcrete; and (3) the salt retaining water within the fine capillarypores of the cement paste. The salt inhibits diffusion of excess waternot used in hydration of cement from the pores of the cement paste,thereby causing the surface of the hardened concrete to more quicklyachieve a desired internal humidity compared to hardened concrete madeusing the salt.

Examples of metal cations that may be suitable for salts in certainembodiments of the invention include, but are not limited to, lithium,potassium, sodium, alkaline earth metals, and combinations thereof.Examples of anions that may be suitable for salts in certain embodimentsof the invention include, but are not limited to, acetate, sulfate,thiosulfate, bromide, chloride, thiocyanate, nitrite, nitrate,hydroxide, silicate, and combinations thereof. Further pursuant to thesecertain embodiments useful salts include, but are not limited to, sodiumacetate (NaAc), sodium nitrate (NaNO₃), sodium nitrite (NaNO₂),potassium carbonate (KCO₃), sodium sulfate (Na₂SO₄), potassium sulfate(K₂SO₄), sodium chloride (NaCl), sodium silicate (NaSiO₃), sodiumthiosulfate hydrate (Na₂S₂O₃.5H₂O), and sodium thiocynate (NaSCN).

Without intending to be bound by theory, an advantage to incorporatingone or more water soluble salts into cement paste to yield faster dryingconcrete may be the sequestration of most of the mix water in the smallpores that exist within the concrete, particularly within cement paste.In certain embodiments of the invention, about 50% of the paste fractionof concrete is made up of capillary and calcium silicate gel pores.Higher cementitious concretes can be about ⅓ by volume, or 9 cubic feetof paste out of the 27 cubic feet in a yard, with the balance being madeup of aggregate, according to certain embodiments of the invention. In aproperly designed mix, according to certain embodiments of theinvention, pore volume can, therefore, account for up to 4½ cubic feetof the water (280 pounds).

A problem that may conventionally be experienced with producing micropores of sufficient quantity to absorb and hold this water in anon-evaporable state is that the size of the pores is typically afunction of the water-cementitious (w/cm) ratio. It is generallyaccepted by a person having ordinary skill in the art that pore sizedoes not substantially exist or become discontinuous, even with extendedcure times, above water-cementitious ratios of about 0.6 or 0.7. As thewater-cement ratio decreases from these levels, smaller pores may beformed. When the water-cement ratio drops below 0.4, sufficient micropores are usually present to impact internal relative humidity and thusmeasurably affect drying time to 75%. This lower level of water dictatesa very stiff (low slump) workability that will not pump easily unlessaugmented with substantial amounts of super-plasticizer, which istolerable in standard weight concrete but, as previously pointed out, isdifficult to manage in lightweight concrete.

Physical upper limits exist on cementitious levels as well, since theirrelative fineness begins to require increasing amounts of water afterthe content surpasses about 800 pounds per cubic yard. In the usualproportions found in lightweight concrete, the aggregate alone can holdfrom 70 pounds to as much as 250 pounds of water. The dichotomy thenbecomes: more cementitious binder cannot be added nor can more watereasily be withdrawn.

In various embodiments of the invention, the cementitious compositionscan include compounds or be compounded to demonstrate a number ofadvantageous properties or features. In an embodiment of the invention,the cementitious compositions include compounds or are compounded toreduce the amount of water of convenience. In other embodiments of theinvention, the cementitious compositions include certain compounds andare compounded in such a way so as to augment the effectiveness of asuperplasticizer. In yet other embodiments of the invention, thecementitious compositions increase packing, or decrease intersticialspacing, of an aggregate that has been included in the composition,thereby effectively reducing permeability. In still yet otherembodiments of the invention, the cementitious compositions includecompounds or are compounded such that the cements that are included inthe composition consume much of the water present, preferably in such amanner so as to reduce excessive production of reaction heat. In certainembodiments, a concrete composition of the invention has an advantage ofimproved workability. In certain embodiments, a concrete composition ofthe invention has a feature of accelerated drying.

In certain embodiments of the invention, the resulting concretecomposition forms a concrete having some of the aforementionedproperties. In other embodiments of the invention, the resultingconcrete composition forms a lightweight concrete having at least someof the aforementioned properties. In certain embodiments of theinvention, the resulting concrete composition forms a low densityconcrete have at least some of the aforementioned properties.

The inventive cementitious compositions, without intending to be boundby theory, offer improvements over other cementitious compositions knownin the art by providing a concrete that demonstrates a reduction in theamount of time needed to achieve a desired water vapor emission rate,otherwise known herein as an “attenuated water vapor emission” or“decreasing the rate of water vapor emission.” In an embodiment of theinvention, the cementitious composition having a decreased rate of watervapor emission from concrete achieves a water vapor emission rate ofbetween about 3 lb/1000 ft²·24 h to about 5 lb/1000 ft²·24 h in lessthan or equal to about 50 days, less than or equal to about 36 days,less than or equal to about 30 days, less than or equal to about 28days, less than or equal to about 25 days, less than or equal to about21 days, less than or equal to about 18 days, less than or equal toabout 15 days, less than or equal to about 12 days, less than or equalto about 10 days, and less than or equal to about 7 days. Preferredembodiments of the invention are those cementitious compositions thatachieve a water vapor emission rate of about 3 lb/1000 ft²·24 h at anytime less than or equal to about 30 days, more preferably, less than orequal to about 25 days, and, even more preferably less than or equal toabout 15 days.

In various embodiments of the invention, the cementitious compositionsprovide a reduction in the number of days needed to achieve an internalrelative humidity of 75%. The cementitious compositions, according tocertain embodiments of the invention, will produce a hardened concretethat has a 75% internal relative humidity in less than about 50 days;preferably, less than about 36 days; more preferably, less than about 30days; even more preferably, less than about 28 days; still even morepreferably, less than about 22 days; and, yet still even morepreferably, less than about 17 days.

In certain embodiments of the invention, the cementitious compositionsoffer the improvement of providing a finished concrete that allows theapplication of coatings and adhesives much sooner than concretesproduced by conventional cementitious compositions known in the art.

In a preferred embodiment of the invention, the cementitiouscompositions are used to prepare a concrete structure for a flooringapplication. While not intending to be bound by theory, upon being mixedwith water, the cementitious compositions consume and emit water in sucha manner that little water remains in the hardened concrete to disturbwater-based glues that are affixed to or coated onto the hardenedconcrete, which act as floor coverings.

The inventors have discovered that it is important not only to reducethe need for the amount of excess water to be added to the cementitiouscomposition in preparing a cementitious mix, but to also include certaincompounds in the formulation and to compound the formulation of thecementitious compositions in such a way that excess water is morefavorably and rapidly removed than that which can be achieved byconventional cementitious compositions.

In various embodiments of the invention, the cementitious compositionsmay include compounds or be compounded to demonstrate a number ofadvantageous features and/or properties. In an embodiment of theinvention, the cementitious compositions include compounds or arecompounded to reduce the amount of water of convenience. In otherembodiments of the invention, the cementitious compositions includecertain compounds and are compounded in such a way so as to augment theeffectiveness of a superplasticizer. In yet other embodiments of theinvention, the cementitious compositions increase packing, or decreaseinterstitial spacing, of an aggregate that has been included in thecomposition, thereby effectively reducing permeability. In still yetother embodiments of the invention, the cementitious compositionsinclude compounds or are compounded such that the cements that areincluded in the composition consume much of the water present,preferably, in such a manner so as to reduce excessive production ofreaction heat.

In preferred embodiments of the invention, the cementitious compositionsinclude a water vapor attenuation agent, as further described herein. Ina preferred embodiment of the invention, the cementitious composition isformulated to include a water vapor attenuation agent that is a water“scavenger”—i.e., a compound that consumes mix water. Without intendingto be limiting, compounds that are characterized as water scavengers areparticularly useful in embodiments of the invention when a water tocement ratio higher than about 0.3, or more, is needed to achieve acertain desired degree of plasticity or workability for pouring acementitious mix produced from the cementitious composition. Forexample, the inventors have discovered that ultrafine calcium carbonatesand highly reactive pozzolans are particularly useful in scavengingexcess water.

Furthermore, it has been found that a cementitious mix made withcementitious compositions having a highly reactive pozzolan, withoutlimitation, such as metakaolin and/or silica fume, continue to hydrateat relative humidity levels substantially below those cementitious mixesformed from a cementitious composition of a Portland cement, slag, andother pozzolans lending to their ability to scavenge water. In anembodiment of the invention, the water vapor attenuation agent of thecementitious composition is a highly reactive pozzolan; an ultrafinecalcium carbonate, preferably, having an average particle size of lessthan or equal to about 3 microns; and any combination thereof having aconcentration in the range of from about 0.5 wt % to about 25 wt %,preferably, from about 3 wt % to about 18 wt %, and, more preferably,from about 3 wt % to about 13 wt % based on the total weight of thecementitious composition.

In an embodiment of the invention, cementitious compositions having awater vapor attenuation agent that is considered a water scavenger,which may include an ultrafine calcium carbonate, preferably, having anaverage particle size of less than or equal to about 3 microns; a highlyreactive pozzolan; and any combination thereof, are capable of consumingat least about 5, at least about 10, at least about 20, at least about30, at least about 40, and at least about 50 pounds of water per cubicyard of concrete over conventional cementitious mixes.

In yet other embodiments of the invention, smaller pore formation ispreferred in the finished concrete. Smaller pore formation, depending onthe formulation of the cementitious mix, may lead to a concrete having adecreased rate of or an attenuated water vapor emission earlier in thecuring or hardening process. Without intending to be bound by theory, areduction in pore size results in an inhibition of capillary watermovement, which may lead to lower apparent internal relative humidityand a reduction in the water vapor emission rate. While a lower water tocement ratio would be expected, in certain situations, to reduce thepore size, the inventor has discovered that the use of a shrinkagereducing agent, preferably, in conjunction with a highly reactivepozzolan, such as, for example metakaolin or even silica fume, or inconjunction with an ultrafine calcium carbonate, preferably, having anaverage particle size of less than or equal to about 3 microns, resultsin a cement having a reduction in pore size.

In certain embodiments of the invention, the cementitious compositionsmay comprise soluble ionic salts. Without intending to be bound by thetheory, soluble ionic salts may sequester water based on the principlethat water vapor concentration, and, therefore, the relative humidityover a salt solution is less than that over that of pure water. Watermay be present in both the gas and the liquid phase, whereas thescarcely volatile salt molecules may only be present in the liquidphase. The salt ions dilute the water and hinder the escape of watermolecules into the air—i.e., the presence of the salt ions changes theequilibrium between the vapor and liquid phase. The rate of return ofwater molecules to the liquid surface is proportional to theirconcentration in the gas, where there are no salt ions to interfere. Thesystem therefore adjusts to equilibrium where there are fewer watermolecules in the air than there would be over a pure water surface. Therelative humidity is therefore lower than 100%. Françcois-Marie Raoultdeveloped the following formula to represent this concept:

P=p _(i) *x _(i)

where,

-   -   P=total vapor pressure    -   p_(i)*=vapor pressure of water    -   x_(i)=moles of water/(moles of water+moles of salts)

If, on the other hand, a binary ionic salt such as sodium acetate(anhydrous) is used, then:

x _(i)=moles of water/(moles of water+2*moles of salt)

According to certain exemplary experimental results, the closeness ofresults calculated by Raoult's law is shown by the data in Table 2.

The salts of Table 2 were placed into aqueous solutions in a closedcontainer with an inserted humidity probe and allowed to stabilize over48 hours. Analogizing this data to concrete, if it is assumed that thecementitious materials contain 0.6% alkali as Na2O then in an 800 poundcementitious mix, for example, the moles of NaOH would be as follows:

Na₂O+H₂O=2NaOH,0.006×800×80/62=6.2/40=0.155

TABLE 2 NaNO₂ NaNO₃ NaC₂H₃O₂ Raoult Solution Solution SolutionCalculated RH RH RH RH 1 molar 93 93 93 97 3 molar 82 89 86 90 6 molar75 80 75 82 RH = relative humidity

Additional salt addition may also raise the surface tension of water byabout 5% and create a thickening of the water-ionic layer along thewalls of the pores, thus effectively reducing their volume and providingan enhancement to negative pore pressure forecast by the Kelvinequation. The Kelvin equation can be used to describe the phenomenon ofcapillary condensation due to the presence of a curved meniscus,according to the following formula:

${\ln \frac{P_{v}}{P_{sat}}} = {- \frac{2\; H\; \gamma \; V_{l}}{RT}}$

where,

-   -   P_(v)=equilibrium vapor pressure    -   P_(sat)=saturation vapor pressure    -   H=mean curvature of meniscus    -   γ=liquid/vapor surface tension    -   V₁=liquid molar volume    -   R=ideal gas constant    -   T=temperature

An additional enhancement, although relatively smaller than the previousmentioned effects, is the expansion of the water lubrication capabilityby salt addition of a salt. The data in Table 3 was obtained by addingseveral separate salts to water and observing the expansion ordisplacement that occurred.

TABLE 3 displacement % 1 molar 2.4 3 molar 5.2 6 molar 16

The inventors have found that the combination of the sum of theseeffects permits the construction of a concrete with enhanced capacity tosequester water in a non-evaporable state. As the data set forth inTable 4 demonstrates, excursions well beyond the maximum 0.4water-cement ratio typically required for fast drying and HPC concreteare now possible.

TABLE 4 Grade pounds Type IV 120 pounds pounds ASTM c330 Lightweightpounds pounds Type F ASTM c33 ASTM c33 ½″ moisture cement slag poundsSand #67 Stone Lightweight % dry wt Mix 1 300 300 0 1400 1700 0 n/a Mix2 300 300 0 1400 1700 0 n/a Mix 3 300 300 0 1400 1700 0 28.2 Mix 4 400400 0 1400 0 750 28.2 Mix 5 400 400 0 1400 0 750 28.2 Mix 6 400 400 01400 0 750 28.2 Mix 7 600 0 200 1400 0 750 28.2 Mix 8 600 0 200 1400 0750 28.2 Mix 9 300 300 0 1400 1700 0 n/a Days to Total ASTM W/Cs PoundsSalt Salt Salt Salt F 2170 (Includes Mix NaOH NaNO₂ NaNO₃ NaC₂H₃O₂ 75%lightweight Water pounds pounds pounds pounds IRH W/Cs water). Mix 1 3250 0 0 0  50+ 0.54 0.54 Mix 2 325 0 0 0 20 23 0.54 0.54 Mix 3 325 4 0 020 14 0.54 0.54 Mix 4 325 0 0 0 0  50+ 0.61 Mix 5 325 0 20 0 0 19 0.61Mix 6 325 4 20 0 0 12 0.61 Mix 7 325 4 20 0 0 45 0.61 Mix 8 325 0 0 0 0100+ 0.61 Mix 9 325 0 0 35 0 26 0.54

As can be readily observed, the drying time with both stone andlightweight concretes can be considerably shortened by increasing theconcentration of single or combinations of salts. Care should beexercised to ensure that the salts do not cause efflorescence, reactadversely with the concrete hydration, or strongly deliquesce.

The preponderance of the aggregate and mix water sequestered within thetreated concrete at an internal relative humidity of 75% as is shown inthe data set forth in Table 5.

The data in Table 5 demonstrates that the amount of water remaining infast-dry design lightweight concrete has been reduced to 7.6 ft³ afterreaching an internal relative humidity of 75%

TABLE 5 Mix cement 250 250 F. pounds slag 550 Oven Loss: 361 sand 1400Evaporation: 25 Lightweight 1006 Retained in 116 Concrete: Water 325Total 502 Lightweight 21.4% of dry Wt. Moisture: mix water 0.41 % WaterW/Cs Total W/Cs 0.63 retained in concrete 95 NaNO₂ 35 cubic feet 7.6water retained in concrete @ 75% internal RH: Total Water: 502Chemically bound 23% Water:

The laboratory work with this system showed an unusual result in thatevaporation pans of treated concrete made from the same samples of salttreated concrete reflected the same pattern as the internal relativehumidity (IRH) specimens. It can be concluded from this that theevaporation rate is related to the formation of a discontinuous poresystem and therefore indicative of small pore formations in thecapillary system.

The low water vapor emission rate and relatively fast attainment of 75%IRH in lightweight concrete led to an investigation of volume change inthis type of concrete. Data relating to shrinkage is set forth in Table6.

The volume change of Table 6 was measured in standard ASTM C-157 moldsduring the first 24 hours. One end plate was anchored and the otherplate was left free to move. The mold was lined with thin plastic tominimize friction. An additional stainless steel stud was screwed intothe free end plate so that it passed through the end of the mold. Amagnetically held dial micrometer stem was positioned to indicate anybar movement following initial set. The concrete bar was sealed inplastic after casting. At 24 hours the dial was read and the barstripped from the mold, wrapped completely in 3 layers of plastic sheetwith the embedded steel studs protruding. The bar was then measured instandard ASTM C-157 devices. At 7 days after casting the bar was againmeasured. Any change was added to the 24 hour reading and considered toconstitute autogenous shrinkage. The bar was then unwrapped and allowedto dry for an additional 28 days in a standard lab environment. Dryingshrinkage was computed by comparing the 7 day dimension to the oneobtained after 28 days of drying. A negative number indicates expansion.

TABLE 6 Dry Dry lbs lbs Normal Modified LW HPC Cement 600 400 GGBFS 0400 Type F Ash 200 0 Sand 1250 1400 1/2″ lightweight 0 850 Stone 1700Water 325 325 plasticizer 14 oz. 16 oz. W/C 0.41 0.41 PCF 151 126 AE1.30% 1.3% Total W/C 0.43 0.63 Agg. Water 13 186 NaNO₂ 0 20 NaOH 0 4 7day autogenous % 0.016 −0.001 28 Day air dry % 0.041 −0.003 Total %0.057 −0.004

The lightweight concrete contains plain water while the surroundingmortar contains about a 1.1-1.3 molar initial concentration of binarysalts. As the cement hydrates and this concentration increases, asemi-permeable gel membrane is grown around the coarse lightweightaggregate particles. The salt imbalance causes sufficient osmoticpressure to fill in the voids that normally develop due to chemicalshrinkage and thereby prevents autogenous shrinkage. This type ofconcrete formulation loses very little water before coming toequilibrium with a 50% RH environment. The lightweight water reserve isknown to replenish this loss as well.

The osmotic pressure π, is given by van′t Hoff's formula, which isidentical to the pressure formula of an ideal gas:

π=cRT

where,

-   -   c=molar concentration of the solute,    -   R=0.082 (liter·bar)/(deg·mol), is the gas constant, and    -   T=temperature on the absolute temperature scale (Kelvin).

For example, water that contains 78 gram/liter of sodium nitrite(NaNO2), and sodium hydroxide (NaOH) typical of the mix in the aboveexample, has an ionic concentration of c=2.39 mol/liter. Inserting thevalues into the van′t Hoff formula, for the ambient temperature T=396 K,yields the osmotic pressure:

π=2.39·0.082·296=58 bar=841 psi

The water pressure could have destructive consequences if its sourcewere to be unlimited, but the lightweight holds a finite amount ofrelatively pure solvent and removal of water results in a negativepartial pressure in the lightweight particle sufficient to establishequilibrium.

The data in exemplary samples of Table 7 illustrate the effect of theaddition of salt to stone and lightweight aggregate concrete. Theevaporation rate was measured by weighing 6×6 inch pans of concrete asthey dried. Note that the addition of salt lowered the evaporation rate.

TABLE 7 Cement 300 300 250 250 lbs GGBFS 300 300 550 550 lbs Sand 14001400 1400 1400 lbs ½″ lightweight 0 0 850 850 lbs Stone 1700 1700 0 0lbs Water 325 325 325 325 lbs plasticizer 6 6 16 16 oz W/Cs 0.54 0.540.41 0.41 lb/lb Moisture loss to 73 31 12 14 lbs 75% IRH NaNO₂ 0 20 3535 lbs NaOH 0 4 0 0 lbs

Furthermore, it has discovered that, in addition to their ability toreduce the extent of shrinkage in a cementitious mix, certain shrinkagereducing agents are capable of lowering the apparent internal relativehumidity as well as reducing the moisture vapor emission rate in acementitious mix. Without intending to be bound by theory, the presenceof certain shrinkage reducing agents in the cementitious mix achievesthis result by inhibiting small capillary water movement in thecementitious mix.

In an embodiment of the invention, the water vapor attenuation agent isa shrinkage reducing agent having a concentration in a range of fromabout 0.1 wt % to about 5 wt %, preferably, from about 0.3 wt % to about5 wt %, and, preferably, from about 0.5 wt % to about 3 wt % based onthe total weight of the cementitious composition. In certain embodimentsof the invention, the shrinkage reduction agent is a liquid having aconcentration in a range of from about 4 ounces to about 60 ounces, fromabout 6 ounces to about 48 ounces, and from about 8 ounces to about 36ounces for every 100 pounds of cementitious composition. While theshrinkage reducing agent can be any shrinkage reducing agent known inthe art, preferred shrinkage reducing agents for use in certaincompositions of the invention include polypropylene glycol, anycopolymers thereof, any derivatives thereof, and any combinationthereof.

In certain preferred embodiments of the invention, the water vaporattenuation agent comprises a shrinkage reducing agent and anothercompound, such as a water scavenger, for ultimately consuming the mixwater. Without intending to be limiting, a shrinkage reducing agent willnot necessarily act to consume the mix water. Hence, the combination ofa shrinkage reducing agent and another compound capable of consuming themix water is preferred in certain embodiments of the invention. In apreferred embodiment of the invention, the water vapor attenuation agentcomprises a shrinkage reducing agent and any of a highly reactivepozzolan; an ultrafine calcium carbonate, preferably, having an averageparticle size of less than or equal to about 3 microns; and combinationsthereof. The concentration of the shrinkage reducing agent is from about0.1 wt % to about 5 wt %, from about 0.3 wt % to about 5 wt %, and,preferably, from about 0.5 wt % to about 3 wt %, and the concentrationof any of a highly reactive pozzolan, preferably, silica fume and, morepreferably, metakaolin; an ultrafine calcium carbonate, preferably,limestone having an average particle size of less than or equal to about3 microns, and combinations thereof is from about 0.5 wt % to about 25wt %, preferably, from about 3 wt % to about 18 wt %, and, morepreferably, from about 3 wt % to about 13 wt % based on the total weightof the cementitious composition.

Another aspect of the invention involves provides a cementitiouscomposition or concrete composition having water soluble salts in thecement paste and cementitious mixtures by infusing a porous lightweightaggregate with a water-salt solution to yield a treated porouslightweight aggregate having improved water saturation and waterretention. According to an embodiment of the invention, it may beadvantageous and desirable to anticipate and accommodate the amount ofwater available in excess of that needed to react with the cements, aswell as the resulting salt concentration in the cement paste. If wateris made available to the mix by virtue of its being absorbed and thendesorbed by lightweight aggregate, then the introduction of water shouldbe anticipated by adjusting the ionic concentration.

According to an embodiment of the invention, the porous lightweightaggregates may be treated with salts or solutions of salts. The treatedaggregates may be mixed with cementitious materials, admixtures, andwater to manufacture various concrete mixtures, which can be used inapplications where ordinary low-density concretes are suitable. Incertain embodiments, pretreatment of lightweight aggregates permitsretention of water in their small capillary pores, thus retaining waterduring storage, as well as facilitating rapid large capillary porerewetting when making fresh concrete.

One method, according to an embodiment of the invention, involvesinfusing porous lightweight aggregates with water to yield treatedporous lightweight aggregates having improved water saturation and waterretention. This method may comprise providing a porous lightweightaggregate having pores and capillaries, and treating the porouslightweight aggregate with an aqueous solution comprising water and atleast one salt. Without intending to be bound by theory, the salt mayenhance penetration of aqueous solution into pores and capillaries ofthe porous lightweight aggregate and help retain water within thecapillaries over time. In various embodiments of the invention, theporous lightweight aggregates are treated with salts by soaking orquenching the aggregates in an aqueous solution of the salt.

A porous lightweight aggregate having improved water saturation andwater retention can be manufactured according to a method comprising:(1) providing a porous lightweight aggregate having pores andcapillaries and (2) treating the porous lightweight aggregate with anaqueous solution comprising water and at least one salt. The at leastone salt enhances penetration of the aqueous solution into the pores andcapillaries of the porous lightweight aggregate and helps retain waterwithin the capillaries over time, as compared to the porous lightweightaggregate treated with only water without the salt.

Another aspect of the invention provides a method of manufacturingfreshly mixed concrete having improved workability comprising: (1)providing a porous lightweight aggregate infused with an aqueoussolution comprising water and at least one salt, and (2) preparing afresh concrete mixture by blending the porous lightweight aggregate withhydraulic cement and water. Without intending to be bound by theory, thesalt may enhance penetration of the aqueous solution into pores andcapillaries of the porous lightweight aggregate and help retain waterwithin the capillaries over time compared to the porous lightweightaggregate only treated with water without the salt. The treated porouslightweight aggregate can lead to enhanced workability of fresh concretecompared to fresh concrete made using the porous lightweight aggregatewithout treatment with the salt.

Another aspect of the invention relates to a method of manufacturinglow-density hardened concrete having improved drying characteristics,comprising: (1) providing a porous lightweight aggregate infused with anaqueous solution comprising water and at least one salt; (2) preparing afresh concrete mixture by blending the porous lightweight aggregate withhydraulic cement and water; and (3) allowing the water to react with thehydraulic cement to form crystalline hydration products, which hardensthe fresh concrete mixture to form the low-density hardened concrete.According to an embodiment of the invention, the at least one salt usedin this method may lead to enhanced initial penetration of the aqueoussolution into the pores and capillaries of the porous lightweightaggregate and helps retain water within the capillaries over time. Thesalt, according to an embodiment of the invention, may inhibit or slowdiffusion of water from the porous lightweight aggregate, therebycausing the hardened concrete to more quickly achieve a desired internalhumidity compared to hardened concrete made using the porous lightweightaggregate in the absence of the at least one salt. Slow release of waterover time may promote internal curing of the cementitious binder,particularly at low water-to-cement ratios, thereby increasing strengthand durability over time, according to certain embodiments of theinvention.

An aspect of the invention provides a concrete manufactured according tothe methods provided herein. In an embodiment of the invention, aconcrete formed from a cementitious composition or cementitious mixturehaving a lightweight aggregate treated with water-soluble solutions asprovided herein may result in: (1) high or nearly complete saturation ofthe pores and capillaries of lightweight aggregates with water duringtreatment, (2) prolonged water retention by the treated porousaggregates to better survive and prevent premature drying duringshipment and storage, (3) improved workability of freshly mixed concretesince the infused aggregates will absorb little, if any, of the wateradded during mixing to provide desired workability, (4) limiting releaseof water and/or water vapor from the porous aggregates during and afterhardening of the concrete structure, thereby enabling low-densityconcrete to attain and maintain a desired level of internal relativehumidity (e.g., 75% or below) within a shorter period of time, and (5)slow release of water from the porous aggregates over time after theconcrete has reached a desired level of internal relative humidity topromote “internal curing” of the cement binder over time, which canincrease concrete strength, particularly in low water-to-cement ratioconcrete.

In other embodiments of the invention, the water vapor attenuation agentmay comprise a water soluble salt that is an inorganic accelerator. Incertain preferred embodiments of the invention, the inorganicaccelerator includes one or more of an alkali metal halide salt. Forexample, the alkali metal halide salt may be any of a sodium halide, apotassium halide, a lithium halide, and any combination thereof. Inpreferred embodiments of the invention, the halide group may berepresented by a chloride or a bromide. Indeed any combination of alkalimetal chloride salts and alkali metal bromide salts may be included inthe cementitious composition.

In an embodiment of the invention, the cementitious compositioncomprises an alkali metal nitrite salt. In certain embodiments of theinvention, the cementitious composition comprises any combination of theaforementioned inorganic accelerators further combined with the alkalimetal nitrite salt. In certain preferred embodiments, the ratio ofalkali metal halide salts to alkali metal nitrite salts is such that thehalide and nitrite ion concentration is substantially the same in thecementitious mix. In other embodiments of the invention, the inorganicaccelerator itself may be an alkali metal nitrite salt, an alkali metalnitrate salt, and any combination thereof. Pursuant to theseaforementioned embodiments, the alkali metal nitrite salt may be asodium nitrite.

In certain embodiments of the invention, the halide group may besubstituted by a pseudo halogen, such as a thiocyanate. Theconcentration of alkali metal halide salts in the cementitious mix,expressed based on a sodium chloride equivalent, may be in a range offrom about 0.2 wt % to about 4 wt %, preferably, from about 0.5 wt % toabout 2.5 wt %. For example, if sodium nitrite were to be used as theinorganic accelerator in the cementitious composition, its concentrationwould be in a range of from about 0.24 wt % to about 4.72 wt %,preferably, from about 0.59 wt % to about 2.95 wt %—i.e., theconcentrations based on sodium chloride expressed above multiplied bythe molecular weight of sodium nitrite and divided by the molecularweight of sodium chloride. In certain embodiments of the invention, thesodium nitrite has a concentration at most about 7.5 wt %. In certainother preferred embodiments of the invention, the concentration ofsodium nitrite is from about 1.0 wt % to about 7.5 wt %. In yet certainother embodiments of the invention, the cementitious compositioncomprises at least one of an alkali metal halide salt, an alkali metalnitrate salt, and an alkali metal nitrite salt having a concentration offrom about 1.0 wt % to about 7.5 wt %. In still certain otherembodiments of the invention, the cementitious composition comprises atleast one of a sodium nitrite having a concentration of from about 1.0wt % to about 7.5 wt %.

In certain embodiments of the invention, the inventors have discoveredthat the mass-based presence of an alkali metal halide salt may be morepreferred especially since the mass of the remaining cementitious mixmay be influenced by the other compounds and their varying densities.For example, according to an embodiment of the invention, an amount ofalkali metal halide salts in the cementitious mix may be from about 10pounds per cubic yard (“pcy”) to about 60 pcy. In other embodiments ofthe invention, the amount of alkali metal halide salts in thecementitious mix may be from about 15 pcy to about 50 pcy. In stillother embodiments of the invention, the amount of alkali metal halidesalts in the cementitious mix may be from about 20 pcy to about 40 pcy.

According to certain embodiments of the invention, an amount of at leastone of an alkali metal halide salt, an alkali metal nitrate salt, and analkali metal nitrite salt in the cementitious mix may be from about 10pcy to about 60 pcy. In other embodiments of the invention, the amountof at least one of an alkali metal halide salt, an alkali metal nitratesalt, and an alkali metal nitrite salt in the cementitious mix may befrom about 15 pcy to about 50 pcy. In still other embodiments of theinvention, the amount of at least one of an alkali metal halide salt, analkali metal nitrate salt, and an alkali metal nitrite salt in thecementitious mix may be from about 20 pcy to about 40 pcy.

According to certain other embodiments of the invention, an amount ofsodium nitrite in the cementitious mix may be from about 10 pcy to about60 pcy. In other embodiments of the invention, the amount of sodiumnitrite in the cementitious mix may be from about 15 pcy to about 50pcy. In still other embodiments of the invention, the amount of sodiumnitrite in the cementitious mix may be from about 20 pcy to about 40pcy.

In certain embodiments of the invention, the amount of any of an alkalimetal halide salt; at least one of an alkali metal halide salt, analkali metal nitrate salt, and an alkali metal nitrite salt; or sodiumnitrite may vary depending upon the type of cement used in thecementitious mix. In certain other embodiments of the invention, theamount of any of an alkali metal halide salt; at least one of an alkalimetal halide salt, an alkali metal nitrate salt, and an alkali metalnitrite salt; or sodium nitrite may vary depending upon the types ofcompounds and even perhaps their concentrations in the cementitious mix.Having the benefit of this disclosure, drying curves may be developed bya person having ordinary skill in the art, similar to those shown inFIGS. 9-11, for example, which are discussed in more detail in theexamples, to determine the amount of any of an alkali metal halide salt;at least one of an alkali metal halide salt, an alkali metal nitratesalt, and an alkali metal nitrite salt; or sodium nitrite.

By way of example, but without intending to be limiting, the dryingcurve of FIG. 9 shows that perhaps the most appropriate amount of sodiumnitrite to be used in the cementitious mix is on the order of about 20lb/yd³. On the other hand, the drying curve of FIG. 10 shows that forthis type of cement, which is different than the cement used in thesamples of FIG. 9, the most appropriate amount of sodium nitrite to beused in the cementitious mix is on the order of at least about 30 lb/yd³or maybe up to 40 lb/yd³ depending upon the preferred dryingcharacteristics to be achieved over time.

As further illustrated by the samples in FIG. 8, the presence of anothercompound of the invention may be used to reduce the amount of any of analkali metal halide salt; at least one of an alkali metal halide salt,an alkali metal nitrate salt, and an alkali metal nitrite salt; orsodium nitrite in the cementitious mix. For example, the use of 15% byweight of silica fume in the cementitious mix may reduce the amount ofsodium nitrite used in the cementitious mix from about 30 lb/yd³ toabout 20 lb/yd³.

The cementitious compositions of the invention may be formulated by aproper selection of any combination of a cement; a binder and/or filler,including any pozzolan; an adjuvant and/or an additive; an aggregate;and a water vapor attenuation agent, as disclosed herein. Thecementitious compositions of the various embodiments of the inventionmay comprise a superplasticizer, even more preferably, a polycarboxylatesuperplasticizer.

In an embodiment of the invention, the cementitious composition includesa cement. In certain embodiments of the invention, the cement is anyhydraulic cement. Non-limiting examples of hydraulic cements suitablefor use in certain cementitious compositions of the invention includeany class of Portland cement; masonry cement; alumina cement; refractorycement; magnesia cements, such as magnesium phosphate cement andmagnesium potassium phosphate cement; calcium-based cements, such ascalcium aluminate cement, calcium sulfoaluminate cement, and calciumsulfate hemi-hydrate cement; natural cement; hydraulic hydrated lime;any complex derivative thereof; and any combination thereof.

Aggregates useful in the cementitious compositions of the inventioninclude, but are not limited to, sand, stone, gravel, and anycombination thereof. Aggregates may be further classified as coarseaggregates that include, for example, gravel, crushed stone, or ironblast furnace slag, and fine aggregates, which typically include a sand.As non-limiting examples, stone can include limestone, granite,sandstone, brownstone, river rock, conglomerate, calcite, dolomite,serpentine, travertine, slate, bluestone, gneiss, quarizitic sandstone,quartizite, and any combination thereof.

Other specialty aggregates include heavyweight aggregates andlightweight aggregates. Heavyweight aggregates can include, but are notlimited to, barite, magnetite, limonite, ilmenite, iron, and steel.

Common lightweight aggregates that are found in certain embodiments ofthe invention include, but are not limited to, slag, fly ash, silica,shale, diatomonous shale, expanded slate, sintered clay, perlite,vermiculite, and cinders. In certain embodiments of the invention,insulating aggregates may also be used. Non-limiting examples ofinsulating aggregates include pumice, perlite, vermiculite, scoria, anddiatomite. In yet other embodiments of the invention, the cementitiouscomposition may additionally comprise any of the aggregates selectedfrom expanded shale, expanded slate, expanded clay, expanded slag, fumedsilica, pelletized aggregate, processed fly ash, tuff, and macrolite. Instill other embodiments of the invention, an aggregate may comprise amasonry aggregate non-limiting examples of which include shale, clay,slate, expanded blast furnace slag, sintered fly ash, coal cinders,pumice, and scoria.

In certain embodiments of the invention, an aggregate may comprise anycombination of coarse aggregates and fine aggregates. Coarse aggregatesare generally considered those aggregate materials retained on a number4 sieve. Fine aggregates are generally considered those aggregatematerials that pass through the number 4 sieve. For example, refer toASTM C33 (2007), which supersedes ASTM C33 (2003), and ASTM C125 (2007),which supersedes ASTM C 125 (2002) and ASTM C 125 (2000a) standardspecifications for concrete additives for a more comprehensivedescription of how to distinguish between fine aggregates and coarseaggregates.

The cementitious compositions may comprise a cement replacement. Inpreferred embodiments of the invention, the cement replacement comprisesa finely divided material, preferably, the finely divided materialcomprising at least one of a finely divided limestone or a fine calciumcarbonate whose particle size is less than about 75 microns, a finelydivided pozzolan and/or slag whose particle size is less than about 75microns, and a finely divided highly reactive pozzolan whose particlesize is less than about 75 microns. In certain embodiments of theinvention, the finely divided material comprises a finely dividedlimestone or a fine calcium carbonate. In other embodiments of theinvention, the finely divided material comprises a pozzolan, which,without intending to be limiting, reacts with water and the limereleased from cement hydration to form densifying calcium silicates. Incertain embodiments of the invention, the pozzolan may comprise anynatural pozzolan; any artificial pozzolan, such as, for example, a flyash; and any combination thereof. In yet other embodiments of theinvention, the finely divided material comprises a ground slag,preferably, a ground granulated blast furnace slag.

In an embodiment of the invention, the cementitious compositioncomprises a cement replacement. In an embodiment of the invention, thecementitious composition comprises a cement replacement, the cementreplacement comprising a finely divided material. In an embodiment ofthe invention, the finely divided material comprises a fine calciumcarbonate. In a preferred embodiment of the invention, the fine calciumcarbonate has a particle size of less than about 75 microns. In anembodiment of the invention, the finely divided material compriseslimestone fines, and the cementitious composition has a ratio by weightof finely divided material to the total weight of the cementitiouscomposition of from about 0.01 to about 1.0, from about 0.03 to about0.8, from about 0.05 to about 0.8, from about 0.2 to about 0.8, and fromabout 0.3 to about 0.7. In other embodiments of the invention thecementitious composition has a ratio by weight of finely dividedmaterial to the total weight of the cementitious composition of fromabout 0.05 to about 0.4, and from about 0.1 to about 0.3. In a certainpreferred embodiment of the invention, the cementitious composition hasa ratio by weight of finely divided material to the total weight of thecementitious composition of from about 0.03 to about 0.8.

In an embodiment of the invention, the cement replacement may comprise adensifying precursor. As used herein, the term “precursor” refers to acompound, complex or the like that, after at least one of becomingchemically activated, becoming hydrated, or through at least one otherpreparation step becomes converted into a desired form to serve tofurther densify a concrete. In certain embodiments of the invention, thedensifying precursor is a densifying calcium silicate precursor.

In an embodiment of the invention, the finely divided material comprisesa pozzolan and/or a slag. In a preferred embodiment of the invention,the pozzolan and/or the slag have a particle size of less than about 75microns. In another preferred embodiment of the invention, the pozzolanand/or slag have a particle size of less than about 45 microns. In anembodiment of the invention, the finely divided material comprises anyof a pozzolan, such as, for example, a fly ash; a hydraulic addition,such as, for example, a ground granulated blast furnace slag; and anycombination thereof, and the cementitious composition has a ratio byweight of finely divided material to total weight of the cementitiouscomposition of from about 0.05 to about 0.8, from about 0.20 to about0.80, and, preferably, from about 0.13 to about 0.75. In anotherembodiment of the invention, the finely divided material comprises ahighly reactive pozzolan and the cementitious composition has a ratio byweight of finely divided material to total weight of the cementitiouscomposition, preferably, from about 0.05 to about 0.2, and, morepreferably, from about 0.06 to about 0.10. In certain embodiments of theinvention, the finely divided material comprises a pozzolan selectedfrom the group consisting of any natural pozzolan; any artificialpozzolan, such as, for example, a fly ash; and any combination thereof.

In certain embodiments of the invention, the cementitious compositionincludes an admixture and/or additive including such admixtures oradditives that function as accelerators, shrinkage reducing agentsretarders, thickeners, tracers, air-entraining agents, air detrainingagents, corrosion inhibitors, pigments, wetting agents, antifoamingand/or defoaming agents, any polymer that is water soluble, waterrepellants, fibers, damp proofing agents, gas formers, permeabilityreducers, pumping aids, viscosity control additives, other rheologymodifying additives, fungicidal and/or germicidal agents, insecticidalagents, finely divided mineral admixtures, alkali-reactivity reducers,pH control agents and/or buffers, bonding admixtures, strength enhancingagents, shrinkage reduction agents, water reduction additives, and anymixture thereof.

In an embodiment of the invention, in addition to the water vaporattenuation agent, as further described herein, the cementitiouscomposition comprises a cement, preferably, a hydraulic cement, having aconcentration from about 10 wt % to about 80 wt %, and from about 25 wt% to about 70 wt % based on the total weight of the cementitiouscomposition. In certain embodiments of the invention, the cementitiouscomposition comprises a cement, preferably, a hydraulic cement, having aconcentration from about 8 wt % to about 35 wt %, from about 10 wt % toabout 30 wt %, from about 12 wt % to about 25 wt %, and from about 14 wt% to about 21 wt % based on the total weight of the cementitiouscomposition.

In certain embodiments of the invention, the cementitious compositionmay additionally comprise, at least one of any aggregate, a pozzolan,and any combination thereof.

Cementitious compositions of the invention may comprise porous ornon-porous lightweight aggregates or admixture to reduce the density andweight of concretes formed therefrom. Porous lightweight aggregates arereadily available from natural sources and are inexpensive to procure,manufacture and process. Examples of porous light-weight aggregatesinclude, but are not limited to, slag, shale, clay, slate, expandedslag, expanded shale, expanded clay, expanded slate, expanded slag,cinders, scoria, pumice, tuff, perlite, and vermiculite.

The porous lightweight aggregate, in an embodiment of the invention, maybe either structural aggregates having compression strength greater than2500 psi, or non-structural aggregates having compression strength of2500 psi or less. Examples of structural lightweight aggregates includeshale, clay or slate expanded by rotary kiln or sintering; cinders; andexpanded slag. Examples of non-structural lightweight porous aggregatesinclude scoria, pumice, perlite and vermiculite.

In an embodiment of the invention, the cementitious compositioncomprises a fine aggregate having a concentration from about 50 wt % toabout 85 wt %, from about 60 wt % to about 80 wt %, and from about 65 wt% to about 75 wt % based on the total weight of the cementitiouscomposition. In another embodiment of the invention, the aggregatecomprises at least one fine aggregate and at least one coarse aggregatehaving a weight ratio of fine aggregate to total aggregate of from about0.25 to about 1.00, from about 0.30 to about 0.75, from about 0.35 toabout 0.65, from about 0.40 to about 0.55, and from about 0.40 to about0.50. In certain embodiments of the invention, the fine aggregate may bea porous lightweight aggregate.

The water retention of cement paste and/or lightweight aggregate andwater-vapor emission of concrete may be affected by salts dissolved insolutions filling the pores of the aggregates and/or by salts directlyadded to cement paste, according to certain embodiments of theinvention. Salts that form hydrates when exposed to water are preferred,as larger hydrate salts can be deposited in fine pores and aid inimpeding water movement from cement paste and/or aggregates.Furthermore, salts having a critical relative humidity of less than 75%tend to buffer the internal relative humidity, according to certainother embodiments of the invention. If these salts react with the lime(calcium hydroxide) liberated by the cement hydration, an additionalbenefit may be obtained, according to an embodiment of the invention.

Complementary to this, the use of low water-cementitious material (w/cm)ratios, which enhance mortar desiccation rate, will leave substantialamounts of material under-hydrated. Moisture from lightweight particles,as opposed to the pressurized water outflow into the plastic concrete asfree water, in lower w/cm ratio concretes (<0.45), may create an area ofmore completely hydrated material in the interfacial zone. A lowerpermeability may result, encapsulating some of the moisture within thelightweight aggregate particle itself, thereby further preventing watervapor movement into the surrounding mortar.

Non-limiting examples of metal cations for salts used in certainembodiments of the invention include lithium, potassium, sodium,alkaline earth metals, and combinations thereof. Non-limiting examplesof anions of salts used in embodiments of the invention include acetate,sulfate, thiosulfate, bromide, chloride, thiocyanate, nitrite, nitrate,hydroxide, silicate, and combinations thereof. Non-limiting examples ofsalts used in certain embodiments of the invention include sodiumacetate (NaAc), sodium nitrate (NaNO₃), sodium nitrite (NaNO₂),potassium carbonate (KCO₃), sodium sulfate (Na₂SO₄), potassium sulfate(K₂SO₄), sodium chloride (NaCl), sodium silicate (NaSiO₃), sodiumthiosulfate hydrate (Na₂S₂O₃.5H₂O), and sodium thiocynate (NaSCN).

In certain embodiments of the invention, the cementitious compositioncomprises a pozzolan, such as, for example, a fly ash; a groundgranulated blast furnace slag; and any combination thereof having aconcentration from about 5 wt % to about 30 wt %, from about 6 wt % toabout 25 wt %, from about 7 wt % to about 20 wt %, and from about 13 wt% to about 17 wt % based on the total weight of the cementitiouscomposition. In other embodiments of the invention, the cementitiouscomposition comprises a highly reactive pozzolan, such as, for example,metakaolin, silica fume, and the like, including any combinationsthereof, having a concentration from about 0.1 wt % to about 5 wt %, 0.5wt % to about 2.5 wt %, and from about 1.0 wt % to about 2.0 wt % basedon the total weight of the cementitious composition. In certainembodiments of the invention, a material selected from the groupconsisting of a pozzolan, a ground granulated blast furnace slag, andany combination thereof can be a very fine particulate material thatreduces the voidage in the cementitious composition resulting in animproved moisture resistance of the finished concrete.

In certain embodiments of the invention, the cementitious compositioncomprises a fine calcium carbonate having a concentration from about0.03 wt % to about 80 wt %, from about 0.05 wt % to about 25 wt %, fromabout 0.1 wt % to about 15 wt %, and, preferably, from about 0.13 wt %to about 7 wt % based on the total weight of the cementitiouscomposition.

In other embodiments, the inventive cementitious composition comprises adispersant. A non-limiting example of a dispersant includes anypolycarboxylate dispersant, with or without polyether units.Polycarboxylate dispersants include those disclosed in U.S. Pat. Publ.No. 2008/0156225 to Bury, entitled “Rheology Modifying Additive forCementitious Compositions,” fully incorporated herein by reference.Dispersants may additionally include chemicals that function as any oneof a plasticizer, a water reducer, a high range water reducer, afluidizer, an antiflocculating agent, or a superplasticizer. Exemplarysuperplasticizers are disclosed in U.S. Pat. Publ. No. 2008/0087199 toGartner, entitled “Cement Shrinkage Reducing Agent and Method forObtaining Cement Based Articles Having Reduced Shrinkage,” fullyincorporated herein by reference. Dispersants may be selected thatfunction as a superplasticizer.

In an embodiment of the invention, the cementitious composition furthercomprises a superplasticizer. Any superplasticizer disclosed herein orotherwise known in the art may be used in the cementitious compositionsof various embodiments of the invention. In a preferred embodiment ofthe invention, the superplasticizer comprises a polycarboxylateadmixture. A non-limiting example of a commercially availablepolycarboxylate superplasticizer includes GLENIUM® 3000 available fromBASF Corporation. GLENIUM 3000 comprises a polymer with a carbonbackbone having pendant side chains with the characteristic that atleast a portion of the side chains are attached to the carbon backbonethrough a carboxyl group or an ether group. GLENIUM 3000 is a liquid atambient conditions having a specific gravity of approximately 1.08.

For example, using a cementitious mix of 658 lb/yd³ of Type III cement,slump of 6 inches, air content of 5-6%, concrete temperature of 65° F.,and curing temperature of 65° F., it has been reported that GLENIUM 3000provides a greater than 2 times increase in compressive strength inconcrete after 8 hours of curing and an improvement of approximately 30%after 12 hours of curing compared to that of a conventionalsuperplasticizer. For a cementitious mix of 658 lb/yd³ of Type I cement,slump of 8-9 inches, non-air-entrained, concrete temperature of 70° F.,dosage of admixtures adjusted to obtain 30% water reduction, GLENIUM3000 has been shown to reduce the initial set time by as much as 2 hoursand 33 minutes compared to that of a conventional superplasticizer.

In an embodiment of the invention, the superplasticizer is in the formof a liquid. In certain embodiments of the invention, the amount ofsuperplasticizer added to the cementitious composition is from about 2ounces to about 30 ounces, from about 4 ounces to about 24 ounces, fromabout 4 ounces to about 20 ounces, and from about 8 ounces to about 20ounces for every 100 pounds of cementitious composition. In certainpreferred embodiments of the invention, the superplasticizer added tothe cementitious composition is from about 4 ounces to about 16 ounces,more preferably, about 5 ounces to about 8 ounces, and, even morepreferably, about 8 ounces for every 100 pounds of cementitiouscomposition.

In an embodiment of the invention, the cementitious composition maycomprise a water reducer. A non-limiting example of a water reduceradmixture includes POLYHEED® 997, an ASTM C494 type A water reducer,supplied by BASF Corporation. In certain embodiments of the invention,it is more preferred to use a water reducer with a superplasticizer inorder to achieve a greater reduction in the amount of water mixed withthe cementitious composition.

In an embodiment of the invention, the cementitious composition mayadditionally comprise prepuff particles such as those disclosed in U.S.Pat. Publ. No. 2008/0058446 to Guevare et al., entitled “LightweightConcrete Compositions,” fully incorporated herein by reference. In anexemplary embodiment, the prepuff particles are polymer particles havingan average particle size of at least about 0.2 mm, at least about 0.3mm, at least about 0.5 mm, at least about 0.9 mm, and at least about 1mm up to at most about 8 mm, at most about 6 mm, at most about 5 mm, atmost about 4 mm, at most about 3 mm, and at most about 2.5 mm.

As disclosed herein, the cementitious composition is combined withwater, which functions as chemical water or hydration water and asexcess water that, among other things, serves to plasticize thecementitious mix to render it more flowable. In preferred embodiments ofthe invention, the excess water, otherwise known as water ofconvenience, is minimized. In other preferred embodiments of theinvention, water vapor attenuation agents are selected to consume orscavenge certain amounts of the water of convenience. In yet otherpreferred embodiments of the invention, the water of convenience is bothminimized and consumed or scavenged based on the use of certain one ormore water vapor attenuation agents.

While it is well-known in the art to include additives such as aplasticizer, more preferably, a superplasticizer, in order to reduce theamount of water of convenience needed, conventionally, the dependence onexcess water has not been entirely eliminated. For example, conventionalcement mixtures tend to have water to cementitious ratios on the orderof 0.4 or higher. Specialty formulations that include a superplasticizerhave been disclosed that reduce the water to cementitious ratio to 0.25or higher, for example, similar to those compositions disclosed in U.S.Pat. No. 6,858,074 to Anderson et al., entitled “High Early-StrengthCementitious Composition.”

In certain embodiments, the cementitious compositions are combined withwater having a water to cementitious ratio of less that about 0.5, lessthan about 0.4, less than about 0.35, less than about 0.3, and less thanabout 0.25. In certain embodiments of the invention, the cementitiouscompositions are mixed with water in a water to cementitious ratio ofabout 0.2 or higher. In preferred embodiments of the invention, thecementitious compositions are mixed with water in a water tocementitious ratio of from about 0.2 to about 0.25. Based on knowledgeprior to the information provided in this disclosure, a person havingordinary skill in the art would have been motivated merely to minimize,within certain limits, depending on other factors, the water tocementitious ratio of the cementitious mix. However, as this disclosureteaches, the inventive cementitious compositions may be formulated withone or more water vapor attenuation agents that allow higher water tocementitious ratios while still attenuating or decreasing the rate ofwater vapor emissions in the cementitious mix.

Another aspect of the invention provides methods of preparingcementitious compositions. In a preferred embodiment of the invention, acementitious composition prepared according to certain embodiments ofthe invention is used to further prepare a concrete having an attenuatedor decreased rate of water vapor emission after curing or hardening. Ina preferred embodiment of the invention, the cementitious composition isproportioned to achieve rapid drying, which can be measured, forexample, by the ASTM test procedures for vapor emissions or internalrelative humidity, as described herein. In certain other embodiments ofthe invention, the cementitious composition is proportioned to achieve adesired property of a hardened concrete, which preferably can bemeasured using any of the various inventive procedures defined herein.

In an embodiment of the invention, a method for preparing a cementitiouscomposition comprises the steps of mixing a hydraulic cement with awater vapor attenuation agent that may include any of an ultrafinecalcium carbonate, preferably, having an average particle size of lessthan or equal to about 3 microns; a highly reactive pozzolan,preferably, silica fume and, more preferably, metakaolin; a shrinkagereducing agent, preferably, any one of polypropylene glycol, anycopolymer thereof, any derivative thereof, and any combination thereof;an inorganic accelerator, preferably, an alkali metal halide salt, analkali metal pseudo halide salt, an alkali metal nitrate salt, an alkalimetal nitrate salt, preferably, sodium nitrite, and any combinationthereof; and combinations thereof. In an embodiment of the invention,the water vapor attenuation agent has a concentration between about 0.5%to about 18% by weight based on a total weight of cementitiouscompounds. In a preferred embodiment of the invention, the cementitiouscomposition will be used to form a cementitious mix that produces aconcrete having an attenuated water vapor emission rate of between about3 lb/1000 ft² 24 h to about 5 lb/1000 ft²·24 h in less than or equal toabout 30 days, less than or equal to about 25 days, less than or equalto about 21 days, less than or equal to about 18 days, preferably, lessthan or equal to about 15 days, more preferably, less than or equal toabout 12 days, and, even more preferably, less than or equal to about 10days after hardening.

In an embodiment of the invention, the method for preparing thecementitious composition may additionally include the step of adding acement replacement. The cement replacement may comprise a finely dividedmaterial. In an embodiment of the invention, the finely divided materialhas a particle size of less than about 75 microns. For example, a finelydivided material having a particle size of less than about 75 micronsmay be the material retained on a standard sieve having 75 micronopenings. Alternatively, a finely divided material having a particlesize of less than about 75 microns may be the material that passesthrough a standard sieve having a varying plurality of openings of +/−75micron. In another embodiment of the invention, the finely dividedmaterial has a particle size of less than about 45 microns. In yetanother embodiment of the invention, the finely divided materialcomprises a material that passes through a standard sieve size of 200.

In an embodiment of the invention, the finely divided material comprisesa fine calcium carbonate. In another embodiment of the invention thefinely divided material comprises limestone fines, the limestone finescomprising calcium carbonate. Further to this embodiment, thecementitious composition has a ratio by weight of finely dividedmaterial to the total weight of the cementitious composition of fromabout 0.03 to about 0.8, and, alternatively, from about 0.05 to about0.4.

In another embodiment of the invention, the finely divided material isselected from the group consisting of a pozzolan, such as, for example,a fly ash; a ground granulated blast furnace slag; and any combinationthereof. Further to this embodiment, the cementitious composition has aratio by weight of finely divided material to total weight of thecementitious composition of from about 0.03 to about 0.8, and,alternatively, from about 0.15 to about 0.8.

In still another embodiment of the invention, the finely dividedmaterial comprises a highly reactive pozzolan selected from the groupconsisting of silica fume, metakaolin, and any combination thereof.Further to this embodiment, the cementitious composition has a ratio byweight of finely divided material to cement of from about 0.05 to about0.20.

In certain embodiments of the invention, the cement replacementcomprises a densifying precursor. In a preferred embodiment of theinvention, the densifying precursor is a densifying calcium silicateprecursor.

In an embodiment of the invention, the method for preparing acementitious composition includes the step of including asuperplasticizer. The superplasticizer has a concentration in a rangefrom about 4 ounces to about 20 ounces for every 100 pounds of the totalweight of the cementitious composition. In a preferred embodiment of theinvention, the superplasticizer includes a polycarboxylatesuperplasticizer.

In an embodiment of the invention, the method for preparing acementitious composition additionally comprises the step ofincorporating an aggregate in the cementitious composition. In anembodiment of the invention, the aggregate comprises at least one of afine aggregate, a course aggregate, and combinations thereof.

In another embodiment of the invention, a method for preparing acementitious composition comprises the steps of mixing a hydrauliccement with a pozzolan, an aggregate, and a water vapor attenuationagent and adding an admixture comprising a superplasticizer. In apreferred embodiment of the invention, the cementitious composition isused to prepare a cementitious mix that achieves a water vapor emissionrate of 3 lb/1000 ft²·24 h in less than or equal to about 30 days, lessthan or equal to about 25 days, less than or equal to about 21 days,less than or equal to about 18 days, preferably, less than or equal toabout 15 days, more preferably, less than or equal to about 12 days,and, even more preferably, less than or equal to about 10 days.

Another aspect of the invention provides a method for the treatment ofporous aggregates used certain cementitious compositions or concretecompositions of the invention. In an embodiment of the invention,treatment of porous aggregates comprises heating the aggregates andquenching the hot aggregates with a solution of one or more salts. Inalternative embodiments of the invention, porous aggregates may besoaked in solutions without first heating the aggregates. In otherembodiments of the invention, the soaked aggregates may be boiled in thesolution. In certain embodiments of the invention the solution of one ormore salts is an aqueous solution. In certain embodiments of theinvention, the concentration of the one or more salts in the solution isin a range of from about 1% by weight to about 20% by weight base on atotal weight of the solution. In certain other embodiments of theinvention, the concentration of the one or more salts in the solution isin a range of from about 5% by weight to about 20% by weight base on atotal weight of the solution. In yet certain other embodiments of theinvention, the concentration of the one or more salts in the solution isin a range of from about 5% by weight to about 15% by weight base on atotal weight of the solution. In still certain other embodiments of theinvention, the concentration of the one or more salts in the solution isin a range of from about 8% by weight to about 20% by weight base on atotal weight of the solution.

In embodiments of the invention when the aggregates are heated beforequenching by the solution, they can be heated to a temperature higherthan 200° F., more preferably higher than 250° F., and more preferablyin the range of 300-400° F. An example embodiment of the soaking orquenching solution is a solution of sodium acetate in a concentration of1 to 2.5 mol/L. Without intending to be bound by theory, lightweightaggregates treated in this fashion may have extended moisture retention,and the resulting low-density concrete may have an accelerated speed toreach 75% internal relative humidity, improved internal curing and otherenhanced concrete characteristics.

In an embodiment of the invention, a process for treating porousaggregates used in certain cementitious compositions of the inventionutilizes hot finished and sized product or lightweight clinker, andquenches and cools the aggregate in an aqueous chemical bath so that asubstantial amount of the capillaries of the lightweight become filledwith solution. The preferred lightweight or clinker temperature is about350° F. (177° C.). The steam, initially quench generated, may be forcedinto the smaller capillaries where it condenses and fills the smallercapillaries with water. The solute may become dispersed through much ofthis system, increasing the water vapor retention by lowering the vaporpressure and modifying the water in the micro pores (less than 0.01 mm)and in mid-range pores as relatively non-evaporable water. Becausesmaller pores in many lightweights may constitute a substantial amountof the total void system, this sequestered water is infused throughcertain methods of the invention can measurably impact the amountavailable to the mortar system as self-desiccation and atmospheric vaporemissions decrease the internal relative concrete humidity to thedesired 75% range.

In certain embodiments of the invention, salts may be directly attachedto outer surfaces of aggregates (e.g., to improve hydration of thebinder). For instance, certain chemicals or vectors that effect changein the concrete as a consequence of their dissolution into the paste maybe attached to the lightweight aggregate by allowing a short surfacedrying time and then applying the appropriate solution to the aggregateor leaving the soak or quench solution on the surface to evaporate anddeposit its solute. In a preferred embodiment, an example solution toachieve this result comprises 15 wt % NaAc and 5 wt % NaCl.

An aspect of the invention provides porous lightweight aggregatestreated with salt for improved water saturation and water retentionmanufactured. Without intending to be bound by theory, the salt isintended to enhance penetration of aqueous solution into pores andcapillaries of the porous lightweight aggregate and helps retain waterwithin the capillaries over time, as compared to porous lightweightaggregate treated with only water without the salt. Small pores of thelightweight aggregates may be filled with solutions to higher levelsthan typically achievable with the conventional use of water alone. Thesolution-filled aggregates of the invention may retain water in thepores for prolonged periods and may facilitate rewetting of largerpores. According to certain embodiments of the invention, higher levelsof water saturation of the lightweight aggregates may prevent absorptionof water when using a concrete pump, avoiding loss of workability orplasticity. Moreover, such treated porous aggregates yield concrete withlower internal humidity.

Another aspect of the various embodiments of the invention provides acementitious mix comprising any of the cementitious compositions of theinvention. In certain embodiments of the invention, the cementitious mixcomprises an amount of water sufficient to provide a water tocementitious ratio of from about 0.05 to about 0.6; from about 0.1 toabout 0.5; preferably, from about 0.2 to about 0.4; and, morepreferably, from about 0.25 to about 0.35.

In certain embodiments of the invention, the cementitious mix comprisesa hydraulic cement, an aggregate, a cement replacement, a water vaporattenuation agent, water, and a superplasticizer. In a preferredembodiment of the invention, the cement replacement is a densifyingcalcium silicate precursor. In another preferred embodiment of theinvention, the superplasticizer is a polycarboxylate superplasticizer.

According to certain embodiments of the invention, the cementitious mixcomprises a hydraulic cement having a concentration from about 10 wt %to about 30 wt % based on a total weight of cementitious compounds; anaggregate having a concentration from about 25 wt % to about 70 wt %based on the total weight of cementitious compounds; a densifyingcalcium silicate precursor having a concentration from about 3 wt % toabout 80 wt % based on the total weight of cementitious compounds; awater vapor attenuation agent having a concentration from about 0.5 wt %to about 18 wt % based on the total weight of cementitious compounds; anamount of water sufficient to provide a water to cementitious ratio offrom about 0.2 to about 0.4; and a polycarboxylate superplasticizerhaving a concentration from about 4 ounces to about 16 ounces per 100pounds of cementitious compounds.

In an exemplary embodiment of the invention, the cementitious mixcomprises a hydraulic cement having a concentration from about 10 wt %to about 30 wt % based on a total weight of cementitious compounds; anaggregate having a concentration from about 25 wt % to about 70 wt %,preferably, from about 45 wt % to about 65 wt % based on the totalweight of cementitious compounds; a densifying calcium silicateprecursor having a concentration from about 3 wt % to about 80 wt %,preferably, from about 5 wt % to about 25 wt % based on the total weightof cementitious compounds; an amount of water sufficient to provide awater to cementitious ratio of from about 0.2 to about 0.4; and apolycarboxylate superplasticizer having a concentration from about 4ounces to about 16 ounces per 100 pounds of cementitious compounds. Inanother embodiment of the invention, the polycarboxylatesuperplasticizer has a concentration of from about 5 ounces to about 8ounces per 100 pounds of cementitious compounds. In a preferredembodiment of the invention, the cementitious mix is used to prepare aconcrete having an attenuated water vapor emission.

An aspect of the invention provides methods of manufacturing freshlymixed concrete having improved workability and faster surface drying. Anembodiment of a method of the invention comprises: (1) adding a saltdirectly to the concrete mix and/or providing a porous lightweightaggregate infused with an aqueous solution comprising water and at leastone salt; (2) preparing a fresh concrete mixture by blending aggregate,hydraulic cement, salt and water; and (3) permitting the concrete toharden. Without intending to be bound by theory, the salt may enhanceretention of water within the cement paste capillaries and/or the poresof lightweight aggregate over time. A reduced IRH, hastened surfacedrying, and inhibition of autogenous and drying shrinkage may berealized in certain concrete mixes of the invention. The salt may alsoenhance wetting of the pores of a porous lightweight aggregates, whichmay result in an increased workability of the fresh concrete mixturewhen compared to a fresh concrete mixture conventionally made withoutusing the salt.

When using porous aggregates, relatively brief storage of such materialsin normal (50%) atmospheric relative humidity will rapidly desiccateparticles saturated only with plain water. In contrast, aggregatesinfused with aqueous salt solution of the invention loses water byevaporation at a slower rate and quickly rehydrates as large voidsrefill with water to a saturated condition upon contact with concretemix water. The need for additional mix water to compensate for pumppressure workability loss may also be minimized. Further, the concretemix can better accommodate the use of super-plasticizers since the lossof the more efficient plasticized mix water under the influence of pumppressure is minimized. Plasticizers can reduce water contents by 10% ormore, thereby speeding the internal drying process.

After the fresh concrete mixture exits the concrete pump, the saltprevents air-pressurized water from being released back to thenon-aggregate components of the concrete, which allows the freshconcrete to maintain desired workability and avoid problems associatedwith excess water, such as bleeding and segregation. Furthermore, thesalt inhibits or slows diffusion of water from the porous lightweightaggregate and cement paste, thereby causing the hardened concrete tomore quickly achieve a desired internal humidity (e.g., 75% or less)compared to hardened concrete made in the absence of the salt.

Furthermore, the water contained in pores of lightweight aggregates maybe gradually released and react with cementitious binder materials afterthe concrete reaches a desired internal relative humidity, which resultsin prolonged hydration and internal curing and a resulting increase inlong-term strength of the concrete manufactured using the cementitiouscompositions or according to certain methods of the invention.

When structural lightweight aggregates are used to make low-densityconcretes according to the disclosed inventive processes, the resultingconcrete would have density and compressive strength suitable forstructural application, with density in the range of 80-120 lb/ft3 (pcf)and compressive strength in the range of 2500-6000 psi. Whennon-structural lightweight aggregates are used, concretes are suitableas fill concrete or insulating concrete when the density is in the rangeof 50-90 pcf and compressive strength 1000-2000 psi; or as insulatingconcrete when density is smaller than 50 pcf and compressive strength isin the range of 300-1000 psi.

Another aspect of various embodiments of the invention provides methodsof preparing a concrete structure using cementitious compositions of theinvention to form a concrete having an attenuated or reduced water vaporemission upon hardening. In an embodiment of the invention, a particularcuring regimen may be applied to a poured cementitious mix that allowsany excess water to be more quickly emitted or dissipated as theconcrete cures or hardens resulting in a reduced or an attenuated watervapor emission after hardening resulting in a concrete that achieves awater vapor emission rate of between about 3 lb/1000 ft²·24 h to about 5lb/1000 ft²·24 h in less than or equal to about 50 days, less than orequal to about 36 days, less than or equal to about 30 days, less thanor equal to about 28 days, less than or equal to about 25 days, lessthan or equal to about 21 days, less than or equal to about 18 days,preferably, less than or equal to about 15 days, more preferably, lessthan or equal to about 12 days, even more preferably, less than or equalto about 10 days, and, yet even more preferably, less than or equal toabout 7 days.

In an embodiment of the invention, a method for preparing a concretestructure using a cementitious composition comprises the steps of mixinga hydraulic cement and a water vapor attenuation agent; adding any of acement replacement, an admixture, and a superplasticizer; and blendingan amount of water into the cementitious composition to prepare acementitious mix. In a preferred embodiment of the invention, thecementitious mix will produce a hardened concrete having an attenuatedwater vapor emission rate of between about 3 lb/1000 ft² 24 h to about 5lb/1000 ft²·24 h in less than or equal to about 50 days, less than orequal to about 36 days, less than or equal to about 30 days, less thanor equal to about 28 days, less than or equal to about 25 days, lessthan or equal to about 21 days, less than or equal to about 18 days,preferably, less than or equal to about 15 days, more preferably, lessthan or equal to about 12 days, even more preferably, less than or equalto about 10 days, and, yet even more preferably, less than or equal toabout 7 days.

In yet another embodiment of the invention, a method for preparing aconcrete structure using a cementitious composition comprises the stepsof providing the cementitious composition having a hydraulic cement, awater vapor attenuation agent, optionally, a cement replacement, and,optionally, a superplasticizer; and blending an amount of water into thecementitious composition to prepare a cementitious mix. In a preferredembodiment of the invention, the cementitious mix will produce ahardened concrete having an attenuated water vapor emission rate ofbetween about 3 lb/1000 ft²·24 h to about 5 lb/1000 ft²·24 h in lessthan or equal to about 50 days, less than or equal to about 36 days,less than or equal to about 30 days, less than or equal to about 28days, less than or equal to about 25 days, less than or equal to about21 days, less than or equal to about 18 days, preferably, less than orequal to about 15 days, more preferably, less than or equal to about 12days, even more preferably, less than or equal to about 10 days, and,yet even more preferably, less than or equal to about 7 days.

Generally, the method of using the cementitious composition additionallycomprises the steps of using the cementitious mix to form a cementitioussegment or a preform of the concrete structure and curing thecementitious segment or preform of the concrete structure to a hardenedconcrete. Further to this embodiment, the cementitious segment may besubjected to additional processing steps. For example, a trowel may beapplied to the cementitious segment to, for example, smooth the surfaceof the cementitious segment and/or to even the distribution of thecementitious mix in a form.

In certain embodiments of the invention, the methods of use mayadditionally comprise the step of applying a regimen and/or techniquethat facilitates a more rapid curing of the cementitious mix to ahardened concrete. Any technique known in the art may be used to morerapidly cure the cementitious mix. Non-limiting examples of suchtechniques include applying a moisture barrier between a moisture sourceand the formed cementitious segment; maintaining the movement of air atthe surface of the cementitious segment being cured to ensure water thatevolves from the segment is removed; heating, for example, with thermaland/or radiant heat, the cementitious segment being cured; andcontrolling humidity between the moisture barrier and the formedcementitious segment by the maintaining and heating steps.

In an embodiment of the invention, the water vapor attenuation agent mayinclude any of an ultrafine calcium carbonate, preferably, having anaverage particle size of less than or equal to about 3 microns; a highlyreactive pozzolan, preferably, silica fume and, more preferably,metakaolin; a shrinkage reducing agent, preferably, any one ofpolypropylene glycol, any copolymer thereof, any derivative thereof, andany combination thereof; an inorganic accelerator, preferably, an alkalimetal halide salt, an alkali metal pseudo halide salt, an alkali metalnitrate salt, an alkali metal nitrate salt, preferably, sodium nitrite,and any combination thereof; and combinations thereof. In an embodimentof the invention, the water vapor attenuation agent has a concentrationbetween about 0.5% to about 18% by weight based on a total weight ofcementitious compounds.

In an embodiment of the invention, the cement replacement comprises afinely divided material. In certain embodiments of the invention, thefinely divided material has a particle size of less than about 75microns. In an embodiment of the invention, the finely divided materialis a material that passes through a standard sieve size of 200.

In certain embodiments of the invention, the finely divided materialcomprises a cement replacement. In an embodiment of the invention, thefinely divided material comprises a fine calcium carbonate. In anotherembodiment of the invention the finely divided material compriseslimestone fines, the limestone fines comprising calcium carbonate.Further to this embodiment, the cementitious composition has a ratio byweight of finely divided material to the total weight of thecementitious composition of from about 0.03 to about 0.8, morepreferably, from about 0.07 to about 0.4.

In another embodiment of the invention, the finely divided material isselected from the group consisting of a pozzolan, such as, for example,a fly ash; a ground granulated blast furnace slag; and any combinationthereof. Further to this embodiment, the cementitious composition has aratio by weight of finely divided material to cement of from about 0.15to about 0.8.

In still another embodiment of the invention, the finely dividedmaterial comprises a highly reactive pozzolan selected from the groupconsisting of silica fume, metakaolin, and any combination thereof.Further to this embodiment, the cementitious composition has a ratio byweight of finely divided material to cement of from about 0.06 to about0.105.

In certain embodiments of the invention, the cement replacementcomprises a densifying precursor. In a preferred embodiment of theinvention, the densifying precursor is a densifying calcium silicateprecursor.

In an embodiment of the invention, the superplasticizer has aconcentration in a range from about 4 ounces to about 20 ounces forevery 100 pounds of cementitious composition. In a preferred embodimentof the invention, the superplasticizer at least includes apolycarboxylate superplasticizer.

In a preferred embodiment of the invention, the amount of water and aratio by weight of the water vapor attenuation agent to the hydrauliccement, which may encompass any of the other compounds as disclosedherein, are proportioned to hydrolyze the cementitious composition andallow the prepared cementitious mix to achieve a desired level ofplasticity. In another preferred embodiment of the invention, the amountof water and a ratio by weight of the water vapor attenuation agentand/or finely divided material to the hydraulic cement, which mayencompass any of the other compounds as disclosed herein, areproportioned to achieve a desired level of plasticity while achieving adesired property of the concrete. In certain embodiments, the desiredproperty of the concrete is any of minimizing an amount of time neededto achieve a water vapor emission of the concrete, minimizing an amountof time needed to achieve an internal relative humidity of the concrete,a reduced shrinkage of the concrete, a maximum heat of hydration, andany combination thereof. Without intending to be limiting, a reducedshrinkage of the concrete will reduce the curling or warping of theconcrete when used in flooring applications and allow for better controlof joint spacing between concrete segments.

In an embodiment of the invention, the method for preparing acementitious composition additionally comprises the step ofincorporating an aggregate into the cementitious composition. In anembodiment of the invention, the aggregate comprises at least one of afine aggregate, a course aggregate, and any combination thereof.

In another embodiment of the invention, a method for preparing acementitious composition comprises the steps of mixing a hydrauliccement with a water vapor attenuation agent, a pozzolan and anaggregate, adding an admixture comprising a superplasticizer, andblending an amount of water into the cementitious composition to preparea cementitious mix. In a preferred embodiment of the invention, thecementitious mix will produce a hardened concrete having an attenuatedwater vapor emission rate of between about 3 lb/1000 ft² 24 h to about 5lb/1000 ft²·24 h in less than or equal to about 50 days, less than orequal to about 36 days, less than or equal to about 30 days, less thanor equal to about 28 days, less than or equal to about 25 days, lessthan or equal to about 21 days, less than or equal to about 18 days,preferably, less than or equal to about 15 days, more preferably, lessthan or equal to about 12 days, even more preferably, less than or equalto about 10 days, and, yet even more preferably, less than or equal toabout 7 days.

The combination of steps for preparing a cementitious composition foruse in preparing a concrete structure may be varied depending upon thedesired application of the finished concrete structure. For example, inmany circumstances, a concrete structure used in flooring must assurethat a dry substrate is available allowing a coating and/or sealant tobe applied within a reasonable amount of time. While not intending to belimiting, the compositions and methods of the invention are suitable forsuch applications because they provide a relatively fast dryingcementitious mix with an attenuated or reduced water vapor emissionsafter cure. Typically, the cementitious mixes for such applications aretypically characterized by an appropriate mix of cementitiouscompounds—i.e., cement(s), slag(s), water vapor attenuation agent(s),and/or pozzolans—available to react with the residual water allowing thewater vapor emissions to be reduced to about 3 lb/1000 ft²·24 h and aninternal relative humidity of about 75% to be achieved in 45 days. Therule-of-thumb for more conventional compositions is 1 month for everyinch of concrete thickness (e.g., 5 months for a commonly used 5 inchconcrete structure).

Another aspect of the invention provides cementitious compositionsmanufactured using any of the aforementioned methods of the invention.Yet another aspect of the invention provides a concrete manufacturedusing any of the aforementioned methods of the invention.

As disclosed herein, the critical parameters for achieving a relativelyfast drying concrete using the cementitious compositions of theinventions and methods as disclosed herein include any of the water tocementitious ratio; employing a curing technique that is adequate toassure eventual water impermeability; type and amount of the one or morewater vapor attenuation agents included in the cementitious composition;optionally, the use of a sufficiently fine material to create a densemass; and any combination thereof.

As a person having ordinary skill in the art having the benefit of thisdisclosure would understand, care must be exercised in blending anypozzolan in order to control the heat of hydration, or else thermalcracking of the concrete could become problematic rendering, for themost part, the use of any pozzolan virtually ineffective. As a personhaving ordinary skill in the art having the benefit of this disclosurewould further understand, care must also be exercised in proportioningand compounding the cementitious mix. For example, a cementitious mixthat is too sticky will be difficult to pump and finish usingconventional techniques.

EXAMPLES Examples 1-2

The purpose of the tests in EX. 1 were to demonstrate the effect of theconcentration of a polycarboxylate superplasticizer and the use of awater reducer on the use of chemically bound water and the extent ofshrinkage realized by the concrete sample mixes of Table 8.

TABLE 8 Sample 1 Sample 2 Sample 3 Compound/Property Concrete MixPortland Cement, Type I-II, lb 800 517 611 Sand, ASTM C33, lb 1,3001,525 1,500 1 inch Stone, ASTM C33, lb 1,850 1,850 1,850 GLENIUM 3000,oz/100 lb cement 16.0 — 8.0 POLYHEED 997, oz/100 lb cement — 5.3 —Water, lb 225 290 228 water to cement ratio 0.28 0.56 0.37 Air Content,% 1.7 3.4 5.4 Density, lb/ft³ (pcf) 155 147 148 Yield, ft³/yd³ 26.9 28.128.1 Slump, inches >6.00 4.25 5.25

The data in Table 9 shows the shrinkage results for the concrete mixesof the examples. The specimens were tested according to the ASTM C157(2006) protocol. Each shrinkage sample was cured at 73° F. and 100%humidity for 24 hours, and followed by a curing step while immersed inwater for 7 days. Drying was conducted at 50% relative humidity and 73°F.

TABLE 9 Sample 1 Sample 2 Sample 3 Days Drying Shrinkage, % 14 0.01330.0193 0.0133 21 0.0203 0.0290 0.0183 28 0.0227 0.0343 0.0217 35 0.02430.0387 0.0230 42 0.0303 0.0487 0.0300 56 0.0350 0.0560 0.0353The cementitious composition of sample 2, which uses a water reducerinstead of a polycarboxylate superplasticizer shows the greatest amountof shrinkage. The cementitious compositions of samples 1 and 3 show thatthe amount of shrinkage can be somewhat maintained with varyingconcentrations of cement in the composition by changing the proportionof superplasticizer to control the water.

The purpose of the test in EX. 2 was to show that the need foradditional water with an increasing concentration of cement in acementitious composition can be offset by increasing the use of asuperplasticizer and also by increasing the concentration of thesuperplasticizer in the cementitious composition. As the sample mixesillustrated in Table 8 show, sample 3 has 94 lbs more concrete thansample 2, and yet has a much smaller demand for water as a result ofusing a superplasticizer versus that of using a water reducer. Sample 1contains 189 lbs more cement than sample 3 and yet has a lower water tocementitious ratio as are result of increasing the concentration ofsuperplasticizer in the cementitious composition.

Example 3

The purpose of the tests in EX. 3 were to demonstrate the effect of apolycarboxylate superplasticizer on the reduction in the amount of timeneeded to achieve a desired rate of water vapor emissions using theconcrete sample mixes of Table 10.

TABLE 10 Sample 4 Sample 5 Sample 6 Compound/Property Concrete MixPortland Cement, Type I-II, lb 800 517 611 Sand, ASTM C33, lb 1,3001,525 1,500 1 inch Stone, ASTM C33, lb 1,850 1,850 1,850 GLENIUM 3000,oz/100 lb cement 16.0 — 8.0 POLYHEED 997, oz/100 lb cement — 5.3 —Water, lb 225 281 228 water to cement ratio 0.28 0.54 0.37 Air Content,% 3.4 N/A 5.6 Density, lb/ft³ (pcf) 155 146 147 Yield, ft³/yd³ 27.0 28.228.2 Slump, inches >6.00 4.50 5.00

The curing data and number of days required to achieve a water vaporemission rate of 3 lb/1000 ft²·24 hr shown in Table 11 were obtained bycasting each of the samples in a 2 foot×2 foot×5½ inch deep panel linedwith polyethylene. Immediately prior to initial set, each panel wasgiven a steel trowel finish and sealed for the noted cure period at 73°F. Following the cure period, the concrete slabs were unsealed andallowed to dry at 50% relative humidity and 73° F. in a drying room. Thewater vapor emissions data was obtained by averaging two calciumchloride dome tests conducted according to the ASTM F1869 test standard.

TABLE 11 Sample 4 Sample 5 Sample 6 Curing Time, days 28 28 28 DryingTime needed for 17 >50 22 3 lb/1000 ft^(2.)24 hr Emissions, daysThe mixture of sample 5 has a water to cementitious ratio that isgreater than that of samples 4 and 6; however, the sample requiresgreater than 50 days drying in order to achieve a water vapor emissionsrate of 3 lb/1000 ft²·24 hr. The mix of sample 6 shows asuperplasticizer helps to attenuate the water vapor emissions over thatof the water reducer used in the mix of sample 5. Sample 4 shows thatincreasing the concentration of the superplasticizer further reduces theamount of drying time needed to achieve the desired water vaporemissions rate.

Example 4

The purpose of the tests in EX. 4 were to demonstrate the effect of apolycarboxylate superplasticizer along with the presence of a reactivepozzolan on the amount of time needed to reduce the internal relativehumidity to a desired value using the concrete sample mixes of Table

TABLE 12 Sample 7 Sample 8 Sample 9 Compound/Property Concrete MixHanson Cement, Type I-II, lb 517 740 740 Silica Fume, lb — 60 —Metakaolin, lb — — 60 Sand, ASTM C33, lb 1,525 1,200 1,200 Sand, ASTMC33 #67, lb 1,950 1,950 1,950 GLENIUM 3000, oz/100 lb cement — 16.2 16.2POLYHEED 997, oz/100 lb cement 5.0 — — Colloid Defoamer, oz 0.5 0.5 0.5Water, lb 264 186 197 water to cement ratio 0.51 0.23 0.25 MixTemperature, ° F. 65 66 67 Air Content, % 1.3 3.6 1.1 Density, lb/ft³(pcf) 152 156 156 Yield, ft³/yd³ 28.1 26.5 26.7 Slump, inches 5.75flowing flowing

Each sample was cast in a 2 foot×2 foot×5½inch deep panel lined withpolyethylene. Immediately prior to initial set, each panel was given asteel trowel finish and sealed for a 13-day cure period at 73° F.Following the cure period, the concrete slabs were unsealed and allowedto dry at 50% relative humidity and 73° F. in a drying room. Therelative humidity was obtained according to the ASTM F 2170 testprocedure using in situ probes. The curing data and number of daysrequired to achieve an internal relative humidity of 75% for the curedconcrete samples are shown in Table 13.

TABLE 13 Sample 7 Sample 8 Sample 9 Curing Time, days 13 13 13 DryingTime needed to Achieve >63 28 28 75% Relative Humidity, daysThe cementitious composition of sample 7, which used only the waterreducer, produced a concrete having an internal relative humidity of87.3% at the end of 63 days. Samples 8 and 9 comprising silica fume andmetakaolin, respectively, as well as a superplasticizer produced aconcrete that required only 28 days of drying time to achieve aninternal relative humidity of 75%.

Example 5

The purpose of the tests in EX. 5 were to demonstrate the effect ofpartial substitution with a finely divided material (finely dividedlimestone) generally smaller than a U.S. standard sieve size 200. Thesieve produced a finely divided material having a particle size of lessthan about 75 microns. #3 limestone fines represent a finely dividedreactive material, the ASTM C33 sand is a fine aggregate, and theCupertino lime is a coarse aggregate. Samples 10, 11, and 12 of Table 14also include a superplasticizer.

TABLE 14 Sample Sample Sample Sample 10 11 12 13 Compound/PropertyConcrete Mix Cement, lb 500 500 800 500 #3 Limestone Fines, lb — 270 — —Sand, ASTM C33, lb 1,700 1,510  1,450  1,470 Cupertino Lime, St. 1,8001,800  1,800  1,800 ¾, lb GLENIUM 3000, 16  16  16 — oz/100 lb cementPOLYHEED 997, — — — 5 oz/100 lb cement Water, lb 213 172 200 269 waterto cement ratio 0.43    0.34    0.25 0.54 Mix Time, min 20  17  14 10Mix Temperature, ° F. 82  86  89 88 Density, lb/ft³ (pcf) 153 157 157150 Yield, ft³/yd³ 27.5   27.1   27.1 26.9 Slump (Spread), inches 5 (24)  (27) 5¼

The number of days required to achieve a water vapor emission rate of 3lb/1000 ft²·24 hr for the cementitious mixes shown in Table 14 wereobtained by casting each of the samples in a 2 foot×2 foot×5½ inch deeppanel lined with polyethylene. The plates, not subjected to a sealedcure time, were allowed to dry at 50% relative humidity and 73° F. in adrying room. The water vapor emissions data were obtained by using thecalcium chloride dome tests according to the ASTM F1869 test standard.The results are shown in Table 15.

TABLE 15 Sample Sample Sample Sample 10 11 12 13 Drying Time neededfor >53 36 36 >53 3 lb/1000 ft² · 24 hr Emissions, daysAs this data shows, the addition of a finely divided calcium carbonateenables the amount of excess water to be further reduced.

Example 6

The purpose of the tests in EX. 6 were to demonstrate the effect ofpartial substitution with a finely divided material (finely dividedground granulated blast furnace slag and finely divided type F fly ash)generally smaller than a U.S. standard sieve size 200 or particleshaving a size less than about 75 microns along with a superplasticizerin the cementitious compositions using the sample mixes of Table 16.

TABLE 16 Sample Sample Sample Sample Sample 14 15 16 17 18Compound/Property Concrete Mix Cement, lb 800 600 400 560 680 GroundSlag, lb — 200 400 — — Fly Ash - Type F, lb — — — 240 120 Sand, lb 1,3001,300 1,300 1,300 1,300 GLENIUM 3000, oz/100 lb cement 8 8 8 8 8 Water,lb 195 190 190 210 198 water to cement ratio 0.24 0.24 0.24 0.26 0.25Density, lb/ft³ (pcf) 151 150 149 144 148 Yield, cc³ 950 957 960 1006971 Slump (Spread), inches flowing flowing flowing flowing flowing

The sample mixes were analyzed using the mortar method, as furtherdisclosed herein. Mortar of the same workability level as the concreteof the investigation was mixed and cast in 6 inch×6 inch plastic pans toa depth of 1⅝ inches. The samples were cured unsealed for 24 hours andthen sealed for a 14-day cure. Vapor loss measurements were determinedbased on the changes in weight of the samples and is reported in Table17.

TABLE 17 Sample Sample Sample Sample Sample 14 15 16 17 18 Total WaterVapor 3.7 2.9 4.4 7.4 5.6 Loss, grIncreasing the amount of ground granulated blast furnace slag, as shownin samples 15 and 16, resulted in the same water to cementitious ratioand produced a vapor loss in the same range as sample 14, the controlmix. Substitution of type F fly ash in samples 17 and 18 resulted inprogressively higher vapor emissions over the curing period, butrepresent rates that still are within a satisfactory range.

Example 7

The sample mixes of Tables 18A & 18B were used to analyze the variationsin water loss measured from the 6 inch×6 inch mortar samples pans formixes comprising cements and sands from five different regions. Theaverage vapor loss for these samples was 6.34, while the standarddeviation for the sample was 1.08.

TABLE 18A Sample Sample Sample Sample Sample 19 20 21 22 23 Cement, grPermanente, CA 650 — — — — Maryland — 650 — — — Texas — — 650 — —Michigan — — — 650 — Tennessee — — — — 650 Sand, gr Seacheldt 1,4301,430 1,430 1,430 1,430 Maryland — — — — — Texas — — — — — Michigan — —— — — Tennessee — — — — — Glenium 3000, oz/100 lb cement 16 16 16 16 16Water, gr 190 208 208 216 210 water to cement ratio 0.29 0.32 0.32 0.330.32 Density, lb/ft³ (pcf) 149 148 148 146 147 Yield, cc³ 953 968 967985 976 Slump, inches 8.0 6.3 6.0 5.5 5.5 Mix Temperature, ° F. 75.076.0 75.0 76.0 75.0 Vapor Loss, gr 8.0 6.3 6.0 5.5 5.5

TABLE 18B Sample Sample Sample Sample 24 25 26 27 Cement, gr Permanente,CA — — — — Maryland 650 — — — Texas — 650 — — Michigan — — 650 —Tennessee — — — 650 Sand, gr Seacheldt — — — — Maryland 1,430 — — —Texas — 1,430 — — Michigan — — 1,430 — Tennessee — — — 1,430 Glenium3000, 35 16 16 16 oz/100 lb cement Water, gr 224 204 216 206 water tocement ratio 0.34 0.32 0.33 0.32 Density, lb/ft³ (pcf) 144 148 146 149Yield, cc³ 1003 970 988 960 Slump, inches 5.0 8.0 5.5 7.3 MixTemperature, ° F. 75.0 76.0 75.0 75.0 Vapor Loss, gr 5.0 8.0 5.5 7.3

Examples 8-9

The purpose of the tests in EX. 8 were to demonstrate the effect of theconcentration of a polycarboxylate superplasticizer and the use of awater reducer on the use of chemically bound water and the extent ofshrinkage realized by the concrete sample mixes of Table 19.

TABLE 19 Sample 28 Sample 29 Sample 30 Compound/Property Concrete MixPortland Cement, Type I-II, lb 800 517 611 Sand, ASTM C33, lb 1,3001,525 1,500 1 inch Stone, ASTM C33, lb 1,850 1,850 1,850 GLENIUM 3000,oz/100 lb cement 16.0 — 8.0 POLYHEED 997, oz/100 lb cement — 5.3 —Water, lb 225 290 228 water to cement ratio 0.28 0.56 0.37 Air Content,% 1.7 3.4 5.4 Density, lb/ft³ (pcf) 155 147 148 Yield, ft³/yd³ 26.9 28.128.1 Slump, inches >6.00 4.25 5.25

The data in Table 20 shows the shrinkage results for the concrete mixesof the examples. The specimens were tested according to the ASTM C157(2006) protocol. Each sample was cured at 73° F. and 100% relativehumidity for 24 hours, and followed by a curing step while immersed inwater for 7 days. Drying was conducted at 50% relative humidity and 73°F.

TABLE 20 Sample 28 Sample 29 Sample 30 Days Drying Shrinkage, % 140.0133 0.0193 0.0133 21 0.0203 0.0290 0.0183 28 0.0227 0.0343 0.0217 350.0243 0.0387 0.0230 42 0.0303 0.0487 0.0300 56 0.0350 0.0560 0.0353The cementitious composition of sample 29, which uses a water reducerinstead of a polycarboxylate superplasticizer, shows the greatest amountof shrinkage. The cementitious compositions of samples 28 and 30 showthat the amount of shrinkage can be somewhat maintained with varyingconcentrations of cement in the composition by changing the proportionof superplasticizer to control the water.

The purpose of the test in EX. 9 was to show that the need foradditional water with an increasing concentration of cement in acementitious composition can be offset by increasing the use of asuperplasticizer and also by increasing the concentration of thesuperplasticizer in the cementitious composition. As the sample mixesillustrated in Tables 19 and 20 show, sample 30 has 94 lbs more concretethan sample 29, and yet has a much smaller demand for water as a resultof using a superplasticizer versus using a water reducer. Sample 28contains 189 lbs more cement than sample 30 and yet has a lower water tocement ratio as a result of increasing the concentration ofsuperplasticizer in the cementitious composition.

Examples 10-12

The purposes of the tests in EXS. 10-12 were to demonstrate the effectsof a shrinkage reducing agent on the reduction in the amount of timeneeded to achieve a desired rate of water vapor emissions, theautogenous shrinkage, and a reduced apparent weight loss due to watervapor using the mortar method with the concrete sample mixes in Table21.

TABLE 21 Sample 31 Sample 32 Compound/Property Concrete Mix cement,lb/yard balance balance metakaolin, lb/yard 60 60 polypropylene glycol,oz/yard — 190 water to cement ratio same same

The data in Table 22 shows the moisture vapor emission rate (MVER) inmeasurement units of lb/1000 ft²·24 h over the drying cycle. The MVER ismeasured using the ASTM F1869 test standard.

TABLE 22 Sample 31 Sample 32 Days Drying MVER, lb/1000 ft² · 24 h 4 7.24.0 8 5.6 3.2 11 3.7 2.5Sample 32, the concrete mix with polypropylene glycol, the shrinkagereducing agent, shows an accelerated attenuation of the moisture vaporemission rate over the drying cycle.

The relative humidity, obtained according to the ASTM F 2170 testprocedure, for these two samples over the drying cycle is shown in Table23.

TABLE 23 Sample 31 Sample 32 Days Drying Relative Humidity, psi 4 79.075.9 7 82.0 81.0 8 81.0 80.0 11 82.0 75.0The difference in relative humidity supports a showing of accelerationin water reduction over the curing cycle for the sample having theshrinkage reducing agent.

The loss in 6×6 inch pan weight attributable to water over the dryingcycle is shown in Table 24.

TABLE 24 Sample 31 Sample 32 Low Average High Low Average High DaysDrying Loss in Pan Weight, lb 1 0.00 0.00 0.00 0.00 0.00 0.00 4 −0.94−0.99 −1.02 −0.22 −0.44 −0.64 6 −1.32 −1.34 −1.36 −0.51 −0.68 −0.86 8−1.65 −1.69 −1.71 −0.68 −0.86 −1.07 11 −2.11 −2.17 −2.19 −0.61 −0.86−1.14The apparent weight loss for the sample having the shrinkage reducingagent is reduced over the drying cycle further confirming that propyleneglycol, the shrinkage reducing agent, acts to decrease the rate of watervapor emissions from the concrete.

Example 13

The purpose of the test in EX. 13 was to demonstrate the effect of apolycarboxylate superplasticizer along with the presence of a reactivepozzolan on the amount of time needed to reduce the internal relativehumidity to a desired value using the concrete sample mixes of Table 25.

TABLE 25 Sample 33 Sample 34 Sample 35 Compound/Property Concrete MixHanson Cement, Type I-II, lb 517 740 740 Silica Fume, lb — 60 —Metakaolin, lb — — 60 Sand, ASTM C33, lb 1,525 1,200 1,200 Sand, ASTMC33 #67, lb 1,950 1,950 1,950 GLENIUM 3000, oz/100 lb cement — 16.2 16.2POLYHEED 997, oz/100 lb cement 5.0 — — Colloid Defoamer, oz 0.5 0.5 0.5Water, lb 264 186 197 water to cement ratio 0.51 0.23 0.25 MixTemperature, ° F. 65 66 67 Air Content, % 1.3 3.6 1.1 Density, lb/ft³(pcf) 152 156 156 Yield, ft³/yd³ 28.1 26.5 26.7 Slump, inches 5.75flowing flowing

Each sample was cast in a 2 foot×2 foot×5½inch deep panel lined withpolyethylene. Immediately prior to initial set, each panel was given asteel trowel finish and sealed for a 13-day cure period at 73° F.Following the cure period, the concrete slabs were unsealed and allowedto dry at 50% relative humidity and 73° F. in a drying room. Therelative humidity was obtained according to the ASTM F 2170 testprocedure using in situ probes. The curing data and number of daysrequired to achieve an internal relative humidity of 75% for the curedconcrete samples are shown in Table 26.

TABLE 26 Sample 33 Sample 34 Sample 35 Curing Time, days 13 13 13 DryingTime needed to Achieve >63 28 28 75% Relative Humidity, daysThe cementitious composition of sample 33, which used only the waterreducer, produced a concrete having an internal relative humidity of87.3% at the end of 63 days. Samples 34 and 35 comprising silica fumeand metakaolin, respectively, as well as a superplasticizer produced aconcrete that required only 28 days of drying time to achieve aninternal relative humidity of 75%.

Example 14

The purpose of the tests in EX. 14 were to demonstrate the effects of anultrafine calcium carbonate—i.e., limestone having an average particlesize less than or equal to about 3 microns—and a highly reactivepozzolan on the reduction in the amount of time needed to achieve adesired rate of water vapor emissions using the concrete sample mixes ofTable 27.

TABLE 27 Sample 36 Sample 37 Sample 38 Sample 39 Compound/PropertyConcrete Mix mortar, lb/yard balance balance balance balance 3 micronlimestone 0 50 100 0 metakaolin, lb/yard 0 0 0 50 water to cement ratiosame same same same curing time, days 45 28 14 7The drying results for these mixes were determined by the mortar methodusing 6×6 inch pans.

As the data in Table 27 shows, the overall curing time needed to achievea water vapor emission rate of about 3 lb/1000 ft²·24 h is reduced byincluding 3 micron limestone (i.e., limestone having an average particlesize of less than or equal to about 3 microns) and metakaolin in thecementitious mix. Increasing amounts of 3 micron limestone furtherdecreases the number of days required to dry the mixture. Metakaolin ofsample 39 provides a larger reduction in drying time than the 3 micronlimestone of samples 37 and 38 when measured on a weight basis.

Example 15

The purpose of the tests in EX. 15 was to demonstrate the effect of aninorganic accelerator on the reduction in relative humidity for thecementitious compositions using the sample mixes of Table 28.

TABLE 28 Sample 40 Sample 41 Sample 42 Compound/Property Concrete Mixcement, lb/yard balance balance balance sodium chloride, lb/yard  0 1120 water to cement ratio same same same days to 75% relative humidity 2919 17

As shown by samples 41 and 42 over control sample 40, concrete mixturescomprising sodium chlorides as an inorganic accelerator, indeed, evenincreasing amounts of the use of the sodium chloride, show a reductionin the amount of time needed to achieve a 75% relative humidity.

Example 16

The purpose of the tests in EX. 16 was to demonstrate the improvement inwater retention of lightweight aggregates treated with the variousaqueous solutions. In EX. 16, lightweight aggregates were heated,quenched, air dried, and re-immersed in water or solutions. Lightweightaggregates of ⅜ inch average diameter were heated to 350° F., thenquenched in 7 different chemical solutions in Samples 44-50, which wereaqueous solutions containing one of NaNO₃, NaNO₂, K₂CO₃, NaAc, Na₂SO₄,K₂SO₄ and NaCl, respectively in each of the samples. Concentrations ofthe solutions were 2.4 mol/L, except for K₂SO₄ (Sample 46), which wasless than 2.4 molar due to solubility limitations. A water quenchedaggregate was provided as a control in Sample 43. The aggregates wereallowed to lab air dry at standard conditions for 27 hours, at 73+/−3°F. and 50% relative humidity.

The efficacy of water retention of the aggregates is inversely indicatedby weight percentage of water loss as shown in FIG. 1. The anhydroussodium acetate (NaAc) of Example 5 reduced the water evaporation toabout 41% of that of plain water.

The same aggregates as in Samples 44-50 were re-immersed in water for 30minutes after being allowed to dry, which is the normal delivery timefor ready-mixed concrete. The solution treated aggregates of theseSamples 51-57 not only lost less water during drying as indicated inFIG. 1, but also re-absorbed more water when re-immersed for 30 minutes,as indicated in FIG. 2, which plots the unfilled water weight percentagerelative to the weight of the aggregates. Assuming the 25% weight gainby quenching with solution indicates full saturation of the lightweight,the graph displays the remaining capillary space in the lightweightafter being placed in the concrete mix prior to pump delivery.

The usual weight of lightweight coarse aggregate per cubic yard ofconcrete ranges from 750 to 900 pounds. If the sodium acetate treatedmaterial of Sample 47 were pumped at high pressure, it is estimated thatthe absorption of free water by the aggregates would be about 28-34pounds. If the water quenched material of Sample 43 were to be utilized,the potential absorption of free water by the aggregates would be about73-88 pounds.

Solution quenching or soaking lightweight aggregates, therefore, willprolong moisture condition during transport and storage. In addition,the air space in the pores of treated lightweight aggregates can be moreeasily and fully filled with water, reducing the quantity and rate ofwater emissions from the concrete in which they are contained.

Example 17

The purpose of the tests in EX. 17 was to demonstrate that evenpartially filling the lightweight pores with various ionic solutesresulted in lower levels of water vapor emission in the low-densityconcrete products. The water-cement ratio was <0.45 in added water basedon saturated surface dried (SSD) aggregates. The water in thelightweight (not included in this calculation) was about 60 additionalpounds. The emissions were obtained from the same concrete mix usingdiffering solute-treated lightweight coarse aggregates. All aggregateswere boiled and cooled in solution, or in the case of the tap water,were soaked for 7 days. The concretes were flushed to remove externaldeposits and then cast in 6×6×2.5 inch rectangular pans, sealed for 3days to cure and then weighed at intervals to measure moisture vaporemissions until they reached the same level of moisture content of 7.8%of dry weight. Vapor loss measurements were determined based on thechanges in weight of the samples and is shown in FIG. 3. The temperaturewas 73° F.+/−3 and about 50% relative humidity.

As shown in FIG. 3, water and four salt solutions were used to treat theaggregates: tap water (H2O, Sample 51), sodium silicate 8 wt % aqueoussolution (NaSi, Sample 52), 20 wt % aqueous solution of anhydrous sodiumacetate (NaAc, Sample 53), 20 wt % aqueous solution of potassium sulfate(K2SO4, Sample 54), and 20 wt % aqueous solution of potassium carbonate(K2CO3, Sample 55). While the concrete made with NaAc treated aggregates(Sample 53) has a water vapor emission of about 12 grams, the concretemade with tap water treated aggregates (Sample 51) has a water vaporemission of about 30 grams.

Example 18

Certain vectors or chemicals that effect change in the concrete as aconsequence of their dissolution into the paste may be attached to thelightweight aggregate by allowing a short surface drying time and thenapplying the appropriate solution to the aggregate or leaving the soakor quench solution on the surface to evaporate and deposit its solute.

The purpose of the tests in EX. 18 was to demonstrate the advantage ofusing the absorbent lightweight as a carrier or vector for materialsthat accelerate hydration of the cementitious medium thereby promotingdensification and hydration. FIG. 4 shows water vapor emission ofconcrete made from aggregates treated by tap water (Sample 56) and foursolutions (Samples 57-60), wherein aggregates were soaked in water(Sample 56) or boiled in aqueous solutions (Samples 57, 58, and 59) orpartially dried then dipped in an aqueous solution of 15% NaAc and 5%NaCl (Sample 60).

Vapor loss measurements are provided in FIG. 4 for concretes made fromboiled and soaked aggregates versus dipped aggregates. The measurementswere determined based on the changes in weight of the samples. Incontrast to Samples 51-55, aggregates were not flushed before beingblended in concrete mixtures.

The “NaAC/NaCl” dipped Sample 60 portrays concrete made with alightweight partially dried (1.8% internal moisture), immersed for 5seconds in the noted solution, allowed to surface dry, and placed in aconcrete mix proportioned the same as the other samples. The notedsolution is an aqueous solution with 15 wt % of sodium acetate and 5 wt% of sodium chloride.

As evident in FIG. 4, the aggregates that were dipped in the notedsolution can be made into a concrete with much lower water vaporemission rate than a concrete made with aggregates treated with wateronly, such that the rate approximates a concrete made from aggregatesboiled and soaked with the same salt solution.

Example 19

The purpose of the test in EX. 19 was to demonstrate the effect of thedirect addition of salt(s) rather than infusion of the aggregates,according to certain other embodiments of the invention.

One or more salts from any of Samples 43-60 are added directly toconcrete having either stone or lightweight aggregate in an amount in arange of about 5 pounds to about 60 pounds of salt (dry weight) percubic yard of concrete, or about 10 pounds to about 50 pounds, or about15 pounds to about 40 pounds per cubic yard of concrete (e.g., in theamounts listed above in Tables 5-7). The resulting concrete provides foradequate drying for application of adhesive or water impermeable coatingwithin 60 days or less.

FIG. 5 is a graph showing representative samples of lightweight concretethat have been tested and which illustrate the close correlation betweenthe water evaporation rate and the number of days required for theconcrete to reach 75% relative humidity. The X axis is the test numberin a sequence of results chosen at random out of 270 tests that wererun. The right vertical axis depicts the number of days required toreach 75% IRH on a test cylinder of concrete with an imbedded humidityprobe. The left vertical axis depicts the mass of water vapor thatescaped from a sample in an evaporative pan made from the same batch.

The data in FIG. 5 illustrates the dichotomy that a higher moisture lossstrongly correlates with a prolonged time to reach a state of 75% IRH.This is the very opposite of standard concrete in which high moistureloss would normally indicate higher drying rate and faster time to reach75% IRH. Since the water contents are the same in each companion sample,it would indicate that the internal pore structure appears to be takingup the available water as it forms, thus inhibiting evaporation as thesmall pores form and reduce internal humidity. As set forth in theresearch described below, the smaller pores contain water that islargely non-evaporable, thus the Kelvin equation reflects this with thepore size controlling the IRH of a system.

Yang, et al., “Self-desiccation mechanism of high-performance concrete,”Research Lab of Materials Engineering, College of Materials Science andEngineering, Tongji University, Shanghai 200433, China, received Jul. 9,2003, revision accepted Mar. 15, 2004, explained the phenomenon asfollows.

Abstract: Investigations on the effects of W/C ratio and silica fume onthe autogenous shrinkage and internal relative humidity of highperformance concrete (HPC), and analysis of the self-desiccationmechanisms of HPC showed that the autogenous shrinkage and internalrelative humidity of HPC increases and decreases with the reduction ofW/C respectively; and that these phenomena were amplified by theaddition of silica fume. Theoretical analyses indicated that thereduction of IRH in HPC was not due to shortage of water, but due to thefact that the evaporable water in HPC was not evaporated freely. Thereduction of internal relative humidity or the so-calledself-desiccation of HPC was chiefly caused by the increase in moleconcentration of soluble ions in HPC and the reduction of pore size orthe increase in the fraction of micro pore water in the total evaporablewater (Tr/Tte ratio).

Autogenous shrinkage is a term that describes the change in volume ofthe concrete that is driven by internal forces as opposed to externalforces such as evaporation or temperature change. Yang, et al. continuein this vein and conclude that “Theoretical analyses and calculationshowed that the reduction of IRH in HPC is not due to shortage of water,but due to the fact that the evaporable water in HPC is not evaporatedfreely. The main reasons behind the reduction of internal relativehumidity or so-called self-desiccation are the increase in moleconcentration of soluble ions and the reduction of pore size or theincrease in the fraction of micro-pore water in the total evaporablewater.” This analysis was based on the availability of ions from thecement assuming soluble alkali cement content of 0.6% as sodium oxide orhydrated, 6 pounds of sodium hydroxide (NaOH) in a mix similar to theHPC mix set forth in Table II above.

Example 20

The purpose of the test in EX. 20 was to illustrate the beneficialeffect on drying time by incorporating hydrophilic salts directly intoconcrete during the mixing process. Samples 61-64 demonstrate shortdrying times using hydrophilic salts in lightweight concrete. Samples65-68 demonstrate short drying times using hydrophilic salts in normalweight concrete. FIG. 6 shows days to 75% humidity for the compositionsof Samples 61-64 having about 1.1 wt % NaNO₂, about 0.3 wt % TS, 0.8 wt% TS, and about 1.25 wt % TS, respectively. FIG. 7 shows days to 75%humidity for the compositions of Samples 65-68 having about 0.28 wt % TSand about 0.09 wt % TC, about 0.28 wt % TS, about 0.55 wt % TS and about0.09 wt % TC, and about 0.55 wt % TS, respectively. (Note: “TS”=SodiumThiosulfate, Na₂S₂O₃.5H₂O, M.W. 248; “TC”=Sodium Thiocyanate, NaSCN, M.W80).

Concrete compositions were made according to Samples 61-68 having thefollowing compositions and data as set forth in Table 8 below.

TABLE 8 Sample Component (lbs) 61 62 63 64 65 66 67 68 Cement 400 400400 400 300 300 300 300 Slag (GGBFS) 400 400 400 400 300 300 300 300ASTM c-33 Sand 1400 1400 1400 1400 1300 1300 1300 1300 Lightweight 17%950 950 950 950 0 0 0 0 water by dry wt. Pea Gravel 0 0 0 0 1700 17001700 1700 Water 325 325 325 325 325 325 325 325 Na₂S₂O₃•5H₂O 0 10 25 4010 10 20 20 NaNO₂ 35 0 0 0 0 0 0 0 NaSCN 0 0 0 0 3.2 0 3.2 0 Other DataTime to 4:10 4:00 3:45 3:00 3:30 3:45 3:30 3:15 Temperature Rise Waterreducer: 2.9 2.9 2.9 2.9 2.9 2.9 2.9 2.9 oz/100 lbs

It has been found that additions of sodium or potassium thiosulfate(known as “hypo” in photography) impart significant acceleration ofhardening to concrete mixtures. This chemical, or mixtures containing itas a partial component, are effective in increasing the rate of internalhumidity reduction. Complementary to this, limited amounts of sodium orpotassium thiocyanate may be used as well. The thiocyanate ion inconcentrations greater than 1% by weight of cement is known create acondition that can be corrosive to reinforcement and is thereforelimited for durability reasons. If the concrete is to be dry in service,larger amounts may be used (assuming prior investigation of galvanicactivity potential).

Example 21

The purpose of the test in EX. 21 was to illustrate the beneficialeffect on relative humidity over time by using sodium nitritesubstantially free of a silica fume in a cementitious mix according toan embodiment of the invention and sodium nitrate and a silica fume in acementitious mix according to another embodiment of the invention.Sample 69 is a cementitious mix having about 30 lb/yd³ of sodium nitritebut substantially free of silica fume. Sample 70 is a cementitious mixhaving about 20 lb/yd³ of sodium nitrite and about 15% by weight of thecementitious mix. FIG. 8 is a graphical representation showing therelative humidity over time for these two exemplary embodiments ofcementitious mixes of the invention. As shown in FIG. 8, Sample 70having silica fume and 20 lb/yd³ of sodium nitrite has about a 4%reduction in average relative humidity in comparison to Sample 69 having30 lb/yd³ of sodium nitrite but being substantially free of silica fume.Indeed, as further shown in FIG. 8, the relative humidity of thecementitious mix having both the sodium nitrite and silica fume beginsto experience relative humidities that are lower than that of Sample 69after about 22 days of drying.

Example 22

The purpose of the test in EX. 22 was to illustrate the beneficialeffect on relative humidity over time by using increasing concentrationsof sodium nitrite in a cementitious mix according to an embodiment ofthe invention. Sample 71 has no sodium nitrite, while samples 72, 73,74, and 75 have 10 lb/yd³, 20 lb/yd³, 30 lb/yd³, and 40 lb/yd³ of sodiumnitrite, respectively. As shown in FIG. 9, which is a chart illustratingthe relative humidity over time for cementitious compositions havingvarious concentration of sodium nitrite according to certain embodimentsof the invention, the cements having greater amounts of sodiumnitrite—i.e., on the order of 30 lb/yd³ to even 40 lb/yd³—exhibit thegreatest relative reductions in relative humidity over the course ofdrying the concrete. As further shown in FIG. 9, the use of these higherconcentrations of sodium nitrite lead to relative humidities that areabout 20% less than the relative humidity of the concrete substantiallyfree of sodium nitrite after about 25 days of drying time. According tothese examples, the use of on the order of 40 lb/yd³ of sodium nitriteresults in a reduction in relative humidity of about 9% in comparison tothe relative humidity of a concrete having about 10 lb/yd³ of sodiumnitrite.

Example 23

The purpose of the test in EX. 23 was to illustrate the beneficialeffect on relative humidity over time by using increasing concentrationsof sodium nitrite in a cementitious mix according to another embodimentof the invention having a different kind of cement than that used in EX22. Sample 76 has no sodium nitrite, while samples 77, 78, 79, and 80have 10 lb/yd³, 20 lb/yd³, 30 lb/yd³, and 40 lb/yd³ of sodium nitrite,respectively. As shown in FIG. 9, which is a chart illustrating therelative humidity over time for cementitious compositions having variousconcentration of sodium nitrite according to certain embodiments of theinvention, the cements having greater amounts of sodium nitrite—i.e., onthe order of 30 lb/yd³ to even 40 lb/yd³—exhibit the greatest relativereductions in relative humidity over the course of drying the concrete.As further shown in FIG. 10, the use of these higher concentrations ofsodium nitrite lead to relative humidities that are about 20% less thanthe relative humidity of the concrete substantially free of sodiumnitrite after about 25 days of drying time. Furthermore, the use of onthe order of 40 lb/yd³ of sodium nitrite results in a reduction inrelative humidity of about 6% in comparison to the relative humidity ofa concrete having about one-half of that concentration of sodiumnitrite. EX. 22 and EX. 23 show the unexpected results that can beachieved based upon the mere differences in types of cement that areused.

Example 24

The purpose of the test in EX. 24 was to illustrate the extent ofreductions in relative humidity over time by using increasingconcentrations of sodium nitrite in a cementitious mix according to yetanother embodiment of the invention. Sample 81 has no sodium nitrite,while samples 82, 83, and 84 have 20 lb/yd³, 30 lb/yd³, and 40 lb/yd³ ofsodium nitrite, respectively. As shown in FIG. 11, which is a graphillustrating the internal relative humidity over time for thecementitious compositions of samples 81-84. In the exemplary examples ofFIG. 11, the cementitious composition of Sample 84 having about 40 pcyor lb/yd³ of sodium nitrite generally provides the lowest internalrelative humidity for these concretes.

All publications mentioned herein, including patents, patentapplications, and journal articles are incorporated herein by referencein their entireties including the references cited therein, which arealso incorporated herein by reference. The publications discussed hereinare provided solely for their disclosure prior to the filing date of thepresent application. Nothing herein is to be construed as an admissionthat the present invention is not entitled to antedate such publicationby virtue of prior invention. Neither should the citation of documentsherein be construed as an admission that the cited documents areconsidered material to the patentability of the claims of the variousembodiments of the invention. Further, the dates of publication providedmay be different from the actual publication dates which may need to beindependently confirmed.

Many modifications and other embodiments of the invention set forthherein will come to mind to one skilled in the art to which thisinvention pertains having the benefit of the teachings presented in thedescriptions herein and the associated drawings. For example, thoughvarious methods are disclosed herein, one skilled in the art willappreciate that various other methods now know or conceived in the artwill be applied to a subject in conjunction with the methods oftreatments or therapies disclosed herein. Therefore, it is to beunderstood that the invention is not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.

1-20. (canceled)
 21. A cementitious composition comprising: a hydrauliccement; an aggregate; and an alkali metal salt selected from the groupconsisting of alkali metal halides, alkali metal nitrites, alkali metalnitrates, alkali metal acetates, alkali metal sulfates, alkali metalthiosulfates, alkali metal thiocyanates, and combinations thereof andhaving a concentration of from about 0.24% to about 4.72% by weight ofthe cementitious composition in order to reduce internal relativehumidity of hardened concrete made from the cementitious composition.22. The cementitious composition of claim 21, wherein the alkali metalsalt has a concentration of from about 0.59% to about 2.95% by weight ofthe cementitious composition.
 23. The cementitious composition of claim21, wherein the alkali metal salt is blended with the cementitiouscomposition.
 24. The cementitious composition of claim 21, furthercomprising water.
 25. The cementitious composition of claim 24, whereinat least a portion of the alkali metal salt is infused as an aqueoussolution in the aggregate.
 26. The cementitious composition of claim 25,wherein the alkali metal salt has a concentration in the aqueoussolution of from about 0.5% to about 18% by weight of the aqueoussolution.
 27. The cementitious composition of claim 21, wherein thealkali metal salt is selected from the group consisting of sodiumacetate, sodium nitrate, sodium nitrite, sodium sulfate, potassiumsulfate, sodium chloride, potassium chloride, sodium thiosulfatehydrate, and sodium thiocyanate.
 28. The cementitious composition ofclaim 21, further comprising a superplasticizer.
 29. The cementitiouscomposition of claim 28, wherein the superplasticizer is selected fromthe group consisting of polycarboxylates; formaldehyde condensates;methylolation and sulfonation products of naphthalene; methylolation andsulfonation products of melamine; methylolation and sulfonation productsof phenol; methylolation and sulfonation products of urea; methylolationand sulfonation products of aniline; metalnaphthalenesulfonate-formaldehyde condensates; metalmelaminesulfonate-formaldehyde condensates; phenolsulfonic acidformaldehyde condensates; phenol-sulfanilic acid-formaldehydeco-condensates; polymers and/or copolymers obtained by polymerizing atleast one monomer selected from the group of unsaturated monocarboxylicacids, derivatives of unsaturated monocarboxylic acids, unsaturateddicarboxylic acids, and derivatives of unsaturated dicarboxylic acids.30. The cementitious composition of claim 21, further comprising afinely divided material.
 31. The cementitious composition of claim 21,further comprising at least one of a pozzolan or granulated blastfurnace slag.
 32. A cementitious composition comprising: a hydrauliccement; an aggregate; and an alkali metal salt selected from the groupconsisting of alkali metal halides, alkali metal nitrites, alkali metalnitrates, alkali metal acetates, alkali metal sulfates, alkali metalthiosulfates, alkali metal thiocyanates, and combinations thereof andhaving a concentration, based on a sodium chloride equivalent, of fromabout 0.2% to about 4% by weight of the cementitious composition inorder to reduce internal relative humidity of hardened concrete madefrom the cementitious composition.
 33. The cementitious composition ofclaim 32, wherein the alkali metal salt has a concentration, based on asodium chloride equivalent, of from about 0.5% to about 2.5% by weightof the cementitious composition.
 34. The cementitious composition ofclaim 32, wherein the alkali metal salt is selected from the groupconsisting of sodium acetate, sodium nitrate, sodium nitrite, sodiumsulfate, potassium sulfate, sodium chloride, potassium chloride, sodiumthiosulfate hydrate, and sodium thiocyanate.
 35. The cementitiouscomposition of claim 32, further comprising water.
 36. The cementitiouscomposition of claim 32, further comprising a superplasticizer.
 37. Thecementitious composition of claim 36, wherein the superplasticizer isselected from the group consisting of polycarboxylates; formaldehydecondensates; methylolation and sulfonation products of naphthalene;methylolation and sulfonation products of melamine; methylolation andsulfonation products of phenol; methylolation and sulfonation productsof urea; methylolation and sulfonation products of aniline; metalnaphthalenesulfonate-formaldehyde condensates; metalmelaminesulfonate-formaldehyde condensates; phenolsulfonic acidformaldehyde condensates; phenol-sulfanilic acid-formaldehydeco-condensates; polymers and/or copolymers obtained by polymerizing atleast one monomer selected from the group of unsaturated monocarboxylicacids, derivatives of unsaturated monocarboxylic acids, unsaturateddicarboxylic acids, and derivatives of unsaturated dicarboxylic acids.38. The cementitious composition of claim 32, further comprising afinely divided material.
 39. The cementitious composition of claim 32,further comprising at least one of a pozzolan or granulated blastfurnace slag.
 40. A cementitious composition for decreasing a rate ofwater vapor emission from a concrete comprising: a hydraulic cement; andan alkali metal salt selected from the group consisting of alkali metalhalides, alkali metal nitrites, alkali metal nitrates, alkali metalacetates, alkali metal sulfates, alkali metal thiosulfates, alkali metalthiocyanates, and combinations thereof and having a concentration offrom about 0.24% to about 4.72% by weight of the cementitiouscomposition in order to reduce internal relative humidity of hardenedconcrete made from the cementitious composition.